JP2006008751A - Ink composition, ink-jet printer using the same, ink-jet printing method, and ink-jet printed image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition sufficiently high in dispersion stability, free of resin component escape from the coloring material, having long-term stability and excellent in intermittent ejectabilty in particular, and to provide an ink tank, ink-jet printer, ink-jet printing method and ink-jet printed images each using such an excellent ink composition. <P>SOLUTION: The ink composition essentially comprises a dispersible coloring material, water, a water-miscible organic solvent and a silicone-based surfactant; wherein the dispersible coloring material comprises a coloring material and electrically chargeable resin pseudo-microparticles smaller in size than the coloring material with both of the two components stuck to each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink composition comprising a dispersible colorant and a silicon-based surfactant, which provides suitable initial ejection performance and a printed image.

  In recent years, the ink jet recording system has features such as high speed, low noise, easy multi-coloring, high flexibility of recording patterns, no need for development and fixing operations, and is rapidly spreading in various applications. In particular, the full-color water-based inkjet recording system technology has undergone remarkable development, and with the demands for further improvement in recording characteristics such as higher recording speed, higher definition, and full color, the improvement of the water-based inkjet recording apparatus and recording method has been improved. Has been done. In general, the performance required for the ink for ink jet recording used in the ink jet recording apparatus is as follows: (1) A uniform image with high resolution and high density without blurring or fogging can be obtained on the paper; 2) Clogging due to ink drying at the nozzle tip does not occur, and ejection responsiveness and ejection stability are always good. (3) Ink fixability is good on paper. (4) Image robustness. Properties (that is, weather resistance, water resistance, etc.) and (5) good long-term storage stability. In particular, with the recent increase in printing speed, there has been a demand for ink that can quickly dry and fix ink and obtain high-quality printing even when printing on plain paper such as copy paper.

  Furthermore, development of water-insoluble color materials, particularly inks using pigments, has been energetically promoted as a color material for water-based inkjet recording inks that can achieve higher weather resistance and water resistance of images. In order to use a water-insoluble color material as an aqueous inkjet recording ink, it is necessary to stably disperse the color material in water. In this case, generally, a method of stabilizing the dispersion using a surfactant or a polymer dispersant (hereinafter also referred to as a dispersion resin) has been used. Further, a method for chemically modifying the surface of the water-insoluble colorant has been proposed (see, for example, Patent Document 1). On the other hand, a microcapsule type pigment in which a pigment is coated with a resin has been proposed (see, for example, Patent Documents 2 and 3). In Patent Document 3, “in a water-based colored fine particle dispersion containing a water-insoluble colorant, the colored fine particle dispersion is added with a vinyl monomer after the water-insoluble colorant is dispersed in an aqueous medium in the presence of the dispersant. When the dispersant is dispersed with a water-insoluble colorant, it exhibits dispersion stability, and when the vinyl monomer is polymerized only in the presence of the dispersant, the stability of the latex that is produced An aqueous colored fine particle dispersion characterized by poor properties ”is disclosed.

  Patent Document 4 proposes a dispersible colorant that is sufficiently high in dispersion stability and does not cause the resin component to be detached from the colorant and is stable for a long period of time, and a simple manufacturing method thereof. Specifically, a dispersible color material composed of a color material and a chargeable resin pseudo fine particle, wherein the color material is dispersed alone with the chargeable resin pseudo fine particle fixed thereto. Ink jet recording inks that provide high dispersion stability and excellent printing characteristics by using color materials have been proposed.

  On the other hand, Patent Document 5 proposes an ink composition using a silicon-based surfactant. These are intended for the excellent surface tension reducing ability, penetration ability, or antifoaming ability of the silicon-based surfactant. In Patent Document 6, in an ink containing a dye, an ethylene oxide adduct of silicon surfactant and acetylene glycol, and a liquid medium, a mass ratio of the silicon surfactant to the ethylene oxide adduct of acetylene glycol It is said that an ink with good uniformity can be obtained when it is in a certain range.

Japanese Patent Laid-Open No. 10-195360 JP-A-8-183920 JP 2003-34770 A Japanese Patent Application No. 2003-428400 JP 05-169790 A JP 2002-80768 A

  When a water-insoluble colorant, particularly a pigment, is used for an ink jet recording ink, it is most important to ensure stable ejection characteristics. In particular, in an on-demand ink jet recording method that is becoming mainstream in recent years, when printing a certain pattern, all the ink dots that form an image are printed equally in order to obtain a high-quality printed matter. It becomes important. However, there is an inconvenience that when one nozzle is not ejected for a certain period of time and the next ejection operation is to be performed subsequently, the first drop of ink is not ejected, or stable ejection is not performed and printing is disturbed. In particular, it has been found that ink jet recording using an ink containing a water-insoluble colorant is often observed. Hereinafter, the discharge of the first drop after the discharge is stopped for a certain period of time is referred to as firing, and a case where some inconvenience occurs in the ejection of the first drop is expressed as poor firing.

  Accordingly, the object of the present invention is to solve these problems of the prior art, have sufficiently high dispersion stability, no detachment of the resin component from the coloring material, and is stable over a long period of time. The object is to provide an excellent ink composition. Furthermore, another object of the present invention is to provide an ink tank, an ink jet recording apparatus, an ink jet recording method, and an ink jet recorded image using such an excellent ink composition.

On the other hand, as a result of intensive studies on the means for solving the above problems, the present inventors have found that a combination of a dispersible colorant having a novel shape and a silicon-based surfactant is sufficient for ink jet recording applications. An ink composition having a stability and dispersion stability, particularly excellent in light emitting properties, and giving a printed matter having high image quality and excellent fastness was obtained. That is, the above object is achieved by the present invention described below. That is, the present invention is as follows.
[1] An ink composition comprising at least a dispersible color material, water, a water-soluble organic solvent, and a silicon-based surfactant. The dispersible color material is smaller than the color material and the color material. An ink composition comprising: a chargeable resin pseudo fine particle, and a dispersible color material formed by fixing the colorant and the chargeable resin pseudo fine particle.

[2] The ink composition according to [1], wherein a plurality of the chargeable resin pseudo fine particles are scattered and fixed to the color material.
[3] The ink composition according to [1] or [2], further including an acetylene glycol surfactant.
[4] The ink composition according to any one of [1] to [3], wherein the silicon surfactant has a solubility in water of 0.5% by mass or more.
[5] The ink composition according to any one of [1] to [4], further comprising a urea derivative as a wetting agent.
[6] Any one of [1] to [5], further comprising at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. Item 4. The ink composition according to item.
[7] The ink composition according to any one of [1] to [6], wherein the content of the silicon surfactant is 0.005% by mass or more and less than 2% by mass.
[8] The ink composition according to any one of [1] to [7], wherein the colorant is a pigment.

[9] An ink tank comprising the ink composition according to any one of [1] to [8].
[10] An ink jet recording apparatus comprising the ink composition according to any one of [1] to [8].
[11] An ink jet recording method comprising forming an image by an ink jet recording apparatus using the ink composition according to any one of [1] to [8].
[12] An ink jet recording image formed by an ink jet recording apparatus using the ink composition according to any one of [1] to [8].

  According to the present invention, a combination of a specific dispersible colorant and a silicon-based surfactant has sufficient ejection stability and dispersion stability for inkjet recording applications, and particularly uses a water-insoluble colorant. Ink composition that gives a printed matter having excellent image quality and high fastness, which is a problem of ink jet recording ink, and an ink tank, an ink jet recording apparatus, an ink jet recording method using the ink composition, And an inkjet recording image is provided.

  As another effect of the present invention, an ink composition excellent in quick drying on a recording medium is provided. As another effect, an ink composition that provides a printed matter with excellent color uniformity, particularly on plain paper, is provided. As another effect, the ink composition is excellent in clogging prevention when used in an ink jet recording apparatus. Is provided. Furthermore, as another effect of the present invention, an ink composition excellent in color development performance particularly on plain paper is provided.

Hereinafter, the present invention will be specifically described with reference to the best mode for carrying out the present invention.
The ink composition according to the present invention can be used for a recording method using a writing instrument such as a pen, an ink jet recording method, and various other printing methods. In particular, the ink composition according to the present invention is suitably used for an ink jet recording method. .

The ink composition according to the present invention includes at least a dispersible color material, water, a water-soluble organic solvent, and a silicon-based surfactant. The dispersible color material includes a color material and the color material. It has small chargeable resin pseudo fine particles, and the color material and the chargeable resin pseudo fine particles are fixed to each other. By combining the dispersible colorant and the silicon-based surfactant, the ink composition using the water-insoluble colorant has ejection stability and dispersion stability suitable for inkjet recording applications, and is particularly easy to emit. An ink composition that gives a printed matter with excellent image quality and excellent fastness is obtained.
The term “dispersible colorant” used in the present specification and claims means that it can be dispersed in water or an aqueous ink medium without essentially adding a surfactant or a polymer dispersant. That is, it is a color material having self-dispersibility.

  The first feature of the ink composition of the present invention includes a dispersible color material composed of a color material and chargeable resin pseudo fine particles, and the color material fixes the chargeable resin pseudo fine particles. In the point. FIG. 1 is a schematic diagram of a dispersible color material, which characterizes the present invention, in which chargeable resin pseudo fine particles 2 are fixed to a color material 1. A portion 2 ′ in FIG. 1B is a portion schematically showing a state in which a part of the chargeable resin pseudo fine particles 2 fixed to the surface of the color material 1 is fused.

  When the chargeable resin pseudo fine particles are fixed to the color material particles, the charge of the charge resin pseudo fine particles is imparted to the surface of the color material, and the dispersible color material can be dispersed in water or an aqueous ink medium. At the same time, the dispersible colorant has excellent adhesion to the recording medium due to the presence of the resin component adhering to the surface. At this time, if the chargeable resin pseudo fine particles, which are characteristic of the dispersible colorant according to the present invention, are not a simple physical adsorption of the resin component, and are in a state of being fixed to the colorant, the chargeable resin pseudofine particles are Since it is not detached from the surface, the dispersible colorant of the present invention is excellent in long-term storage stability.

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

  The state in which the chargeable resin pseudo fine particles are fixed to the color material in the present invention is considered to be due to a strong interaction between the color material surface and the chargeable resin pseudo fine particles. Charged resin pseudo fine particles are formed by intertwining polymers composed of various monomer unit compositions, and these have various structures locally, so their local surface energy is distributed in various states. is doing. The color material and the polymer are firmly bonded in that the surface energy of the color material and the surface energy of the polymer are in good agreement. Furthermore, at the interface where one chargeable resin pseudo fine particle contacts the color material, there are a plurality of points where the surface energies of both coincide locally. It is expected that the fixed state between the color material particles and the chargeable resin pseudo fine particles is established by the strong interaction at the plurality of positions.

  Furthermore, in the inside of the charged resin pseudo fine particles, a strong interaction works between the constituting polymers to form physical crosslinks. For this reason, even when the chargeable resin pseudo fine particles have many hydrophilic groups, the fixed charge resin pseudo fine particles are detached from the coloring material or have hydrophilic groups from the chargeable resin pseudo fine particles. The resin component does not continue to elute. On the other hand, in the encapsulation method as described in Patent Document 2, since the highly hydrophilic resin cannot be strongly bonded to the color material, the resin is detached from the color material, and as a result, the dispersible color material is stored for a long time. In some cases, sufficient stability cannot be obtained.

  In addition, the dispersible colorant contained in the ink composition according to the present invention has a high specific surface area by fixing the chargeable resin pseudo fine particles to the colorant, and the charge of the chargeable resin pseudo fine particles is extremely high. The surface charge of the dispersible colorant can be obtained with high efficiency. That is, it is a form in which more surface charges are more efficiently arranged on the surface of the dispersible colorant, and the resin component as compared to the form in which the colorant is coated with a resin, as represented by Patent Document 2. High dispersion stability can be imparted even when the substantial acid value or amine value of is smaller.

  Furthermore, since the dispersible colorant is dispersed alone with the charged resin pseudo fine particles fixed thereto, it is essentially stable without the aid of other surfactants or polymer dispersants. And a self-dispersing colorant that can be dispersed in an ink liquid medium such as water. Therefore, the dispersible colorant contained in the ink composition according to the present invention is a polymer dispersion agent or other resin component or surfactant component that may be released over a long period of time. It is not necessary to add for the purpose. As a result, the ink composition of the present invention can be an ink composition that can obtain a sufficiently high print density even on a recording medium having high ink permeability, such as plain paper.

  As described above, the ink composition according to the present invention is excellent in that the colorant has 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 high storage stability. Therefore, more preferable results can be obtained when the chargeable resin pseudo fine particles are scattered in large numbers and fixed to the color material. In particular, it is desirable that there is a certain distance between the adhering charged resin pseudo fine particles, and it is preferably distributed uniformly. More preferably, the surface of the coloring material is exposed between the chargeable resin pseudo fine particles. Such a form is confirmed by observing the ink composition of the present invention with a transmission electron microscope or a scanning electron microscope.

As the silicon-based surfactant that is the second feature of the ink composition of the present invention, for example, those having a siloxane bond are preferably used.
When trying to apply the conditions proposed in Patent Document 6 to an ink composition using a water-insoluble colorant, although the improvement in uniformity was observed, the performance was still insufficient. In the present invention, the combination of the dispersible colorant and the silicon-based surfactant exhibits a good one-shot performance regardless of the presence or absence of an acetylene glycol ethylene oxide adduct and the ratio thereof. It became clear.

  Examples of the silicon surfactant used in the present invention include BYK-345, BYK-346, BYK-347, BYK-348 (all manufactured by Big Chemie Japan Co., Ltd.), L-720, L-7001, L-7002, L-7604, FZ-2113, FZ-2105, Y-7006, FZ2120, FZ-2161, Z-2162, FZ-2163, FZ-2164 and FZ-2166 (manufactured by Nihon Unicar) are listed. However, it is not limited to these.

  Although it is not clear how the silicon surfactant contained in the ink composition according to the present invention improves the uniformity of the ink composition containing the water-insoluble colorant, it is expected as follows. 1) The silicon-based surfactant is strongly oriented at the interface between the ink and air present in the vicinity of the ejection opening of the ink jet recording apparatus to prevent moisture evaporation in the ink and to prevent the water-insoluble color material or resin contained in the ink. Prevents the interaction of components, etc., and maintains the fluidity of the ink near the air interface. 2) Improves the wettability of the ink and the member that forms the ink flow path and the discharge port of the ink jet recording apparatus. Reduce friction.

  From the above, among the above-mentioned silicon-based surfactants, those that can quickly reach the ink / air interface or ink / member interface in the ink composition have a higher improvement effect, and the solubility in water is particularly 25 ° C. In this case, a silicon-based surfactant having 0.5% by mass or more gives a more preferable result.

  Furthermore, from the above mechanism, when the ink composition according to the present invention contains a large amount of silicon surfactant, the silicon surfactant is excessively oriented at the ink / air interface, and the fluidity of the ink interface is reversed. There is a risk of losing. In the present invention, the content of the silicon surfactant is preferably 0.005% by mass or more and less than 2% by mass. When the amount is less than 0.005% by mass, the above-mentioned silicon-based surfactant is first adsorbed to a member that forms an ink channel or an ejection port of an ink tank or an ink jet recording apparatus, and sufficient performance cannot be obtained. When the amount is more than 2% by mass, the above-described mechanism may have an adverse effect on the uniformity.

  Further, the point that the ink composition of the present invention has both high printing performance and excellent shot performance is considered as follows. The improvement in the light emission can be seen by adding the above-mentioned silicon-based surfactant, but if the silicon-based surfactant is adsorbed on the water-insoluble colorant in the ink at the same time, the effect of improving the light emission is small. Is expected to be. Therefore, when a pigment dispersed with a polymer dispersant or the color material described in Patent Documents 2 and 3 is used, the silicon-based surfactant is strongly adsorbed to the color material, and in some cases, the color material surface In order to cause exchange adsorption with the polymer dispersant, the polymer dispersant may be released into the ink, and so on, in some cases, sufficient uniformity cannot be obtained. Furthermore, since the coloring material adsorbed with the above-mentioned silicon-based surfactant has high dispersion stability and penetrability on the recording medium, sufficient print density cannot be obtained on plain paper medium having high penetrability. There is.

  On the other hand, the dispersible color material contained in the ink composition according to the present invention is dispersed in the ink in a form in which the chargeable resin pseudo fine particles are fixed on the color material surface as described above. Adsorption of the system surfactant is less likely to occur, and the improvement of the uniformity is exhibited more effectively, and a high printing density can be obtained even on a plain paper medium.

  Furthermore, it has been clarified that the ink composition according to the present invention exhibits excellent quick drying on a recording medium. As described above, the dispersible color material is dispersed in the ink in a form in which the charged resin pseudo fine particles are fixed to the color material surface. When this ink arrives on the recording medium, the solvent in the ink is caused by capillarity on pores on the recording medium (voids between cellulose fibers in the case of plain paper, and in the receiving layer in the case of coated paper and glossy paper). Is absorbed into the pores). At the same time, the ink quickly wets onto the recording medium due to the excellent surface tension reducing ability of the silicon surfactant. At this time, the dispersible colorant according to the present invention has many fine gaps due to the morphological characteristics of the dispersible colorant resin fine particles scattered in the portions where the colorants are in contact with each other. For this reason, the capillary phenomenon also acts on the ink solvent existing between the color materials, and is quickly absorbed into the recording medium.

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

[Color material]
The color material that is a component of the dispersible color material contained in the ink composition of the present invention will be described below. As the coloring material used in the present invention, any known or newly developed coloring material can be used, but preferably a hydrophobic dye, an inorganic pigment, an organic pigment, a metal colloid, a colored resin. It is desirable that the colorant is insoluble in water, such as particles, and can be stably dispersed in water together with the dispersant. Preferably, a coloring material having a dispersed particle size in the range of 0.01 to 0.5 μm (10 to 500 nm), particularly preferably in the range of 0.03 to 0.3 μm (30 to 300 nm) is used. The dispersible color material of the present invention using the color material dispersed in this range is a preferable dispersible color material that gives an image having high coloring power and high weather resistance when used as an aqueous ink.

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

  Examples of organic pigments that can be 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]
The chargeable resin pseudo fine particles, which are another component of the dispersible colorant contained in the ink composition of the present invention, are substantially insoluble in water and are in the water (or ink) of the colorant to be fixed. The dispersion unit (dispersed particle size) in (medium) is small, and is defined as a micro-assembly formed by aggregating resin components having a sufficiently high degree of polymerization. The form of the minute body is pseudo close to a sphere, or a plurality of minute bodies (chargeable resin pseudo fine particles) are arranged within a certain range. It is preferable that the resin components constituting the chargeable resin pseudo fine particles are physically or chemically cross-linked with each other.

  In another preferred embodiment, when the dispersed particle diameter of the chargeable resin pseudo fine particles in water can be measured by, for example, the dynamic light scattering method, the average value of the dispersed particle diameter is preferably 10 nm. It is desirable to be in the range of 200 nm or more. Furthermore, from the viewpoint of long-term storage stability of the dispersible colorant, it is more preferable that the polydispersity index of the dispersed particle diameter is suppressed to less than 0.2. When the center value of the dispersed particle diameter is larger than 200 nm or when the polydispersity index is larger than 0.2, the original purpose of finely dispersing and stabilizing the coloring material may not be sufficiently achieved. Further, when the average value of the dispersed particle diameter is smaller than 10 nm, the form as the chargeable resin pseudo fine particles cannot be sufficiently maintained, and the resin is easily dissolved in water, so that the merit of the present invention cannot be obtained. There is a case. On the other hand, in the range of 10 nm or more and 200 nm or less, the particle 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. .

  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.

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

  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. Classified as hydrophobic monomers, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylate-n-propyl, acrylate-n-butyl, acrylate-t-butyl, benzyl acrylate, methyl methacrylate (Meth) acrylic acid esters such as ethyl methacrylate, isopropyl methacrylate, methacrylate-n-propyl, methacrylate-n-butyl, isobutyl methacrylate, tert-butyl methacrylate, tridecyl methacrylate, benzyl methacrylate, etc. Styrene monomer such as styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-tert-butyl styrene, etc .; itaconate such as benzyl itaconate; dimethyl maleate, etc. Such as Esters; fumaric acid such as fumaric acid esters such as dimethyl 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, methacrylic acid, p-styrenesulfonic acid and salts thereof.

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

  Specific examples of nonionic hydrophilic monomers include, for example, monomers having a radically polymerizable unsaturated bond and a hydroxyl group exhibiting strong hydrophilicity in the structure, and (meth) acrylic. Hydroxyethyl acid, hydroxylpropyl (meth) acrylate, etc. are classified into this. In addition, various known or novel oligomers and macromonomers can be used without limitation.

  Furthermore, it is also preferable to use a crosslinkable monomer. For example, divinylbenzene, allyl (meth) acrylate, methylene bisacrylamide and the like can be mentioned, and other known or novel various crosslinking monomers can also be used.

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

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

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

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

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

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

[Synthesis of chargeable resin pseudo fine particles and fixation to coloring material]
The method for synthesizing the chargeable resin pseudo fine particles and the method for fixing to the color material are carried out by a method for synthesizing the charge resin pseudo fine particles and a method for combining the charge resin pseudo fine particles and the color material. Can do. In particular, the production method described in Patent Document 4 is preferably used. Hereinafter, examples of the method for producing a dispersible colorant according to the present invention, which is preferably implemented in the present invention, will be given.

  First, a water-insoluble colorant is dispersed with a dispersant to prepare a dispersed aqueous solution of the water-insoluble colorant. Next, in this dispersed aqueous solution, the chargeable resin pseudo fine particles and the coloring material are fixed by a step of aqueous precipitation polymerization of the radical polymerizable monomer using an aqueous radical polymerization initiator. The dispersible colorant obtained through this aqueous precipitation polymerization process is a water-insoluble color in which the chargeable resin pseudo fine particles synthesized in the aqueous precipitation polymerization process are strongly and firmly adhered to the colorant. It becomes a material and has excellent dispersion stability by itself. Further, in the above-described aqueous precipitation polymerization process, the characteristics of the chargeable resin pseudo fine particles can be easily controlled to the preferred form as described above. A fixed state with the chargeable resin pseudo fine particles is satisfactorily achieved. Hereinafter, preferred embodiments of the manufacturing method will be described in more detail.

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

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

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

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

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

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

  In addition, as the water-insoluble colorant to be used, the performance of the dispersible colorant obtained by the preferred embodiment of the chargeable resin pseudo fine particles to be fixed can be controlled when it does not have self-dispersibility. This is preferable.

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

[Radical polymerization initiator]
As the radical polymerization initiator used in the present invention, any general water-soluble radical polymerization initiator can be used. Specific examples of the water-soluble radical polymerization initiator include persulfates and water-soluble azo compounds. Or the redox initiator by the combination of a water-soluble radical polymerization initiator and a reducing agent may be sufficient. Specifically, 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, one having an initiator residue that is neutral or anionic is selected. Thereby, the surface charge can be obtained more efficiently. Similarly, when obtaining a dispersible colorant having a cationic group, it is preferable to select one having an initiator residue that is neutral or cationic.

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

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

[Aqueous precipitation polymerization]
Subsequently, a preferred embodiment of the aqueous precipitation polymerization, which is a step of synthesizing the chargeable resin pseudo fine particles, which is a feature of the present invention, and fixing it to the coloring material will be described. In addition, this invention is not restrict | limited at all by embodiment described below. FIG. 2 is a process diagram schematically showing a process flow of the manufacturing method. The process up to obtaining a dispersible colorant by this step is considered as follows. First, as shown in FIG. 2A, a dispersed aqueous solution in which the coloring material 1 is dispersed in the aqueous solution by the dispersant 3 is prepared. At this time, the coloring material is dispersed and stabilized by adsorption of the dispersing agent, and this adsorption is in a thermal equilibrium state. Next, the temperature of the dispersion aqueous solution prepared in FIG. 2A is raised while stirring, and the monomer component 4 is added thereto together with, for example, the aqueous radical polymerization initiator 5 (see FIG. 2B). The added aqueous radical polymerization initiator 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. Although the specific reaction mechanism is described in detail in Patent Document 4, when the reaction of the monomer proceeds, the generated oligomer becomes insoluble in water and precipitates from the aqueous phase to become a precipitate. However, since the oligomers precipitated at this time do not have sufficient dispersion stability, they coalesce to form charged resin pseudo fine particles, and the charged resin pseudo fine particles are further separated from the surface of the coloring material in the aqueous dispersion and hydrophobic. Strongly adsorbed by sexual interaction. At this time, the polymerization reaction continues to proceed inside the chargeable resin pseudo fine particles, and the adsorption with the coloring material is changed to a more energetically stable state to become a fixed state. On the other hand, the coloring material is stabilized by fixing a plurality of chargeable resin pseudo fine particles, and the dispersant in an equilibrium state is detached from the surface of the coloring material.

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

  In the above-described process, 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, the monomer component is preferably an aqueous solution. It is desirable to drop it into a dispersed aqueous solution of a water-insoluble colorant that contains a radical polymerization initiator in advance. Alternatively, it is also desirable to add the water-insoluble colorant dropwise at the same time or separately from the aqueous radical polymerization initiator in the aqueous dispersion. In order to uniformly obtain desired charged resin pseudo fine particles from a mixture of monomers having different properties such as a hydrophobic monomer and a hydrophilic monomer, it is desirable to always keep the copolymerization ratio of the monomers having different properties constant. . When the mixture of monomers is added to the polymerization system in excess of the amount of monomer consumed in the polymerization reaction within a certain time, only a specific monomer species is polymerized in advance, and the remaining monomers are polymerized in advance. There is a tendency to polymerize after the consumed monomer is consumed, and in this case, a large non-uniformity occurs in the properties of the generated chargeable resin pseudo fine particles.

  Furthermore, when the resin component has a high content of the hydrophilic monomer component, it may not be precipitated due to its high hydrophilicity, and may remain in the system as a water-soluble resin component without forming charged resin pseudo fine particles. is there. On the other hand, by dropping the monomer component into a water-insoluble colorant-dispersed aqueous solution containing an aqueous radical polymerization initiator, the copolymerization ratio of the hydrophobic monomer and the hydrophilic monomer is always kept constant, and the desired copolymer is maintained. Chargeable resin pseudo fine particles composed of a polymerization 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 the ink composition according to the present invention is prepared using the water-insoluble color material in which the chargeable resin pseudo fine particles fixed to the color material, obtained in the above-described step, is further purified in addition to the above steps. It is desirable to do. In particular, in the above, it is possible to carry out purification treatment on unreacted polymerization initiator, monomer component, dispersant, water-soluble resin component that has not been fixed, and chargeable resin pseudo fine particles, etc. Is important in maintaining high. As a purification method to be used, an optimum one may be selected from generally used purification methods. For example, purification using a centrifugal separation method or an ultrafiltration method is 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 having undergone the process of the present invention has a large surface even if the amount of the anionic monomer used in the above process is relatively small. A functional group density can be obtained and high dispersion stability can be imparted. As a result, it becomes possible to increase the dispersion stability of the chargeable resin pseudo fine particles without impairing the long-term storage stability.

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

  In the ink composition of the present invention, the presence or absence of an acetylene glycol surfactant is not a problem from the viewpoint of uniformity, but includes an acetylene glycol surfactant particularly from the viewpoint of improving the color uniformity of a plain paper medium. That is preferred. Preferably, 0.1% by mass to 5% by mass, and more preferably 0.1% by mass to 3% by mass with respect to the ink is added.

  In the ink composition of the present invention, further containing a wetting agent is a preferable form in terms of improving the clogging resistance of the ink. In particular, it is preferable to contain a urea derivative as a wetting agent. The content of the urea derivative as the wetting agent is 0.1% by mass or more and 20% by mass or less, preferably 0.2% by mass or more and 15% by mass or less with respect to the ink.

  In the ink composition of the present invention, further comprising a pyrrolidone derivative is a preferable form because the printing density on plain paper can be further increased. In particular, when at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone is included, a further improvement in the light emission can be achieved simultaneously with a high print density. Seen and preferred. The content thereof is 0.2% by mass or more and 20% by mass or less, and preferably 0.5% by mass or more and 15% by mass or less with respect to the ink.

  In the ink composition of the present invention, the surface zeta potential of the dispersible colorant in the aqueous medium constituting the ink composition, particularly when it has an anionic group, has an average value of -20 mV or more and -80 mV or less. In the case of having a cationic group, it is another preferred embodiment that the average value is in the range of +10 mV to +60 mV. By setting the surface zeta potential within the above range, excellent long-term storage stability as a water-based ink can be imparted. On the other hand, when the zeta potential is in the range of −15 mV to +10 mV, the high dispersion stability of the dispersible colorant is hindered by the action of the aqueous medium, and the long-term storage stability of the aqueous ink may be insufficient. On the other hand, when the zeta potential is smaller than −80 mV or larger than +60 mV, the storage stability of the ink is excellent, but the water resistance of the printed matter may be insufficient.

  In a state in which the water-insoluble color material is dispersed and stabilized in the ink, the dispersed state is maintained by preventing the color materials from approaching each other due to the zeta potential of the water-insoluble color material. In the dispersion stability and storage stability of ink for ink jet recording, the zeta potential is an important physical property value.

  Furthermore, the absolute value of the zeta potential not only greatly contributes to dispersion stability, but also its distribution should be considered. In particular, in a dispersion system in which colloidal dispersions having different zeta potentials coexist, even if the zeta potential has the same sign (positive or negative), the dispersion surface having a small absolute value and the absolute value being large There is known a hetero-aggregation phenomenon that facilitates aggregation due to an attractive force between the surfaces of the dispersion. That is, the zeta potential of the dispersible colorant in the water-based ink according to the present invention also exhibits an effect on dispersion stability because the absolute value is uniform. According to the study by the present inventors, it is preferable that the zeta potential of the dispersible colorant of the present invention is less than 50 with a standard deviation with respect to the average value, because desirable dispersion stability can be obtained.

[Recorded image]
The ink jet recording image according to the present invention is formed on a recording medium by an ink jet recording apparatus as will be described later, using the ink composition of the present invention containing the dispersible colorant having the above-described configuration. The recording medium used in the present invention can be used without limitation even if it is a medium capable of ink jet recording.

[Image recording method and recording apparatus]
The dispersible color material and the water-based ink containing the color material according to the present invention are used in an ink jet discharge type head, and also as an ink tank in which the ink is stored or an ink for filling the ink tank It is also effective. 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 a so-called on-demand type and a continuous type. In particular, in the case of the on-demand type, the ink is disposed corresponding to a sheet or a liquid path holding ink. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding the nucleate boiling to the electrothermal transducer, heat energy is generated in the electrothermal transducer, and the thermal action of the recording head This is effective because the film can be boiled on the surface and, as a result, the drive signals can be made to correspond one-to-one and bubbles in the ink can be formed. By the growth and contraction of the bubbles, ink is ejected through the ejection openings to form at least one droplet. It is more preferable that the drive signal has a pulse shape, because the bubble growth and contraction is performed immediately and appropriately, and thus ink discharge with particularly excellent responsiveness can be achieved. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by adopting the conditions described in US Pat. No. 4,313,124, which is an invention relating to the rate of temperature increase of the heat acting surface.

  As the configuration of the recording head, in addition to the combination configuration (linear liquid channel or right-angle liquid channel) of the discharge port, the liquid channel, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting part The present invention is also effective for configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose configurations in which the lens is disposed in a bending region. In addition, the present invention is also effective for a configuration (JP-A-59-123670, etc.) in which a common discharge hole is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters. . 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 the satisfying configuration or the configuration as a single recording head formed integrally may be used, but the present invention can exhibit the above-described effects more effectively.

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

  Next, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “parts” and “%” are based on mass unless otherwise specified, and the numerical values in the table represent mass%.

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

  Next, 100 parts of the pigment dispersion 1 obtained above was used, and the following mixture was gradually added dropwise with stirring with a motor in a state heated to 70 ° C. in a nitrogen atmosphere, and polymerization was performed for 5 hours. It was. The mixture consists of 5.5 parts of methyl methacrylate, 0.5 part of acrylic acid, 0.12 part of potassium hydroxide, 0.05 part of potassium persulfate and 20 parts of water. The obtained dispersion was diluted 10-fold with water and centrifuged at 5,000 rpm for 10 minutes to remove the aggregating component. Then, it further refine | purified by centrifuging on conditions of 12,500 rpm and 2 hours, and the dispersible color material 1 which is a sediment was obtained.

This dispersible colorant 1 is dispersed in water, centrifuged at 12,000 rpm for 60 minutes, and the precipitate redispersed in water is dried, and then scanned with an electron microscope JSM-6700 (JEOL Hi-Tech). When the dispersible colorant 1 was observed at a magnification of 50,000 times, a state where the resin fine particles were fixed to the surface of the carbon black was observed. In addition, also about the color material after this described in a present Example, the form of the color material was confirmed with the method similar to the above.
The dispersible colorant 1 obtained above was mixed so as to have the component composition shown in the following table, and further filtered under pressure with a membrane filter having a pore size of 2.5 microns to obtain the recording ink 1 of this example. Prepared. The total amount of ink was adjusted with water (ion exchange water) so as to be 100 parts. The same applies to the subsequent inks.

[Example 2]
The recording ink 2 according to this example was produced as follows. First, a mixed liquid having a composition consisting of 10 parts of pigment blue (PB) 15: 3 (manufactured by Clariant), 6 parts of glycerin, 10 parts of a styrene-acrylic acid dispersant and 74 parts of water as a colorant Dispersion was performed at 1,500 rpm for 5 hours in a sand mill manufactured by Kogyo Co., Ltd. to obtain pigment dispersion 2. In the sand mill, zirconia beads having a diameter of 0.6 mm were used, and the filling rate in the pot was 70%. The styrene-acrylic resin used as the dispersant was a copolymer having a copolymerization ratio of 70:30, Mw = 8,000, and an acid value of 170. The obtained pigment dispersion 2 was stably dispersed with an average dispersion particle size of 108 nm, and the polydispersity index was 0.14.

  Next, 100 parts of the pigment dispersion 2 obtained above was used, and in a state heated to 70 ° C. under a nitrogen atmosphere, a mixed liquid having the following composition was gradually added dropwise while stirring with a motor to carry out polymerization. It was. The mixed solution used above consists of 5.7 parts of methyl methacrylate, 0.3 part of acrylic acid, 0.07 part of potassium hydroxide, 0.05 part of potassium persulfate and 20 parts of water. After polymerization for 5 hours as described above, the obtained dispersion was diluted 10-fold with water, centrifuged at 5,000 rpm for 10 minutes to remove aggregated components, and then 12, It refine | purified by centrifuging on conditions of 500 rpm and 2 hours, and the dispersible color material 2 which is a sediment was obtained. Further, in the same manner as in Example 1, the dispersible colorant 2 obtained above was mixed so as to have the component composition shown in the following table, and further pressurized with a membrane filter having a pore size of 2.5 microns. Filtration was performed to prepare a recording ink 2 of this example.

[Example 3]
The recording ink 3 according to this example was produced as follows. First, a mixed liquid having a composition comprising 10 parts of Pigment Yellow (PY) 74 (manufactured by Clariant) as a coloring material, 6 parts of glycerin, 10 parts of a styrene-acrylic acid-based dispersant, and 74 parts of water is used. Dispersion was carried out at 1,500 rpm for 5 hours in a sand mill manufactured to obtain pigment dispersion 3. In the sand mill, zirconia beads having a diameter of 0.6 mm were used, and the filling rate in the pot was 70%. The styrene-acrylic resin used as the dispersant was a copolymer having a copolymerization ratio of 70:30, Mw = 8,000, and an acid value of 170. The obtained pigment dispersion 3 was stably dispersed with an average dispersion particle size of 126 nm, and the polydispersity index was 0.16.

Next, 100 parts of the above pigment dispersion 3 was used, and while being heated to 70 ° C. in a nitrogen atmosphere, a mixed liquid having the following composition was gradually added dropwise while stirring with a motor to perform polymerization. The mixture comprises 5.7 parts of methyl methacrylate, 0.3 part of acrylic acid, 0.07 part of potassium hydroxide, 0.05 part of potassium persulfate and 20 parts of water. After polymerization for 5 hours as described above, the obtained dispersion was diluted 10-fold with water, centrifuged at 5,000 rpm for 10 minutes to remove aggregated components, and then 12, By centrifuging at 500 rpm for 2 hours, a dispersible colorant 3 as a sediment was obtained.
The mixture was mixed so as to have the composition shown in the following table, and further filtered under pressure through a membrane filter having a pore size of 2.5 microns to prepare a recording ink 3 of this example.

[Example 4]
The recording ink 4 according to this example was produced as follows. First, a mixed liquid having a composition comprising 10 parts of Pigment Red (PR) 122 (manufactured by Ciba Specialty Chemicals) as a coloring material, 6 parts of glycerin, 10 parts of a styrene-acrylic acid dispersant, and 74 parts of water, The pigment dispersion 4 was obtained by dispersing for 5 hours at 1,500 rpm in a sand mill manufactured by Kanada Rika Kogyo Co., Ltd. In the sand mill, zirconia beads having a diameter of 0.6 mm were used, and the filling rate in the pot was 70%. The styrene-acrylic resin used as the dispersant was a copolymer having a copolymerization ratio of 70:30, Mw = 8,000, and an acid value of 170. The obtained pigment dispersion 4 was stably dispersed with an average dispersion particle size of 96 nm, and the polydispersity index was 0.13.

Next, 100 parts of the pigment dispersion 4 was used, and a mixture having the following composition was gradually added dropwise while stirring with a motor in a state heated to 70 ° C. in a nitrogen atmosphere to carry out polymerization. The mixed solution comprises 5.7 parts of methyl methacrylate, 0.3 part of acrylic acid, 0.07 part of potassium hydroxide, 0.05 VA-057 (manufactured by Wako Pure Chemical Industries, Ltd.) and 20 parts of water. After polymerization for 5 hours as described above, the obtained dispersion was diluted 10-fold with water, centrifuged at 5,000 rpm for 10 minutes to remove aggregated components, and then 12, The dispersible colorant 4 which is a sediment was obtained by centrifuging at 500 rpm for 2 hours.
The mixture was mixed so as to have the composition shown in the following table, and further filtered under pressure through a membrane filter having a pore size of 2.5 microns to prepare a recording ink 4 of this example.

[Example 5]
Using 100 parts of the same pigment dispersion 1 prepared in Example 1 and heating to 70 ° C. under a nitrogen atmosphere, the following mixture is gradually added dropwise with stirring with a motor, and polymerized for 5 hours. Went. The mixed solution used above consists of 17.2 parts of methyl methacrylate, 0.8 part of sodium p-styrenesulfonate, 0.05 part of potassium persulfate and 20 parts of water. After the polymerization, purification was performed by centrifugation in the same manner as in Example 1 to obtain a dispersible colorant 5. The mixture was mixed so as to have the composition shown in the following table, and further filtered under pressure with a membrane filter having a pore size of 2.5 microns to prepare a recording ink 5 of this example.

[Example 6]
Using 100 parts of the same pigment dispersion 1 prepared in Example 1 and heating to 70 ° C. in a nitrogen atmosphere, a mixed solution having the following composition was gradually added dropwise while stirring with a motor, and polymerization was performed. Went. The mixture used consisted of 5.7 parts of benzyl methacrylate, 0.3 part of acrylic acid, 0.07 part of potassium hydroxide, 0.01 part of potassium persulfate and 20 parts of water. After the polymerization for 5 hours as described above, the mixture was purified by centrifugation under the same conditions as in Example 1 to obtain a dispersible colorant 6 as a precipitate. The mixture was mixed so as to have the composition shown in the following table, and further filtered under pressure through a membrane filter having a pore size of 2.5 microns to prepare a recording ink 6 of this example.

[Example 7]
Using 100 parts of the same pigment dispersion 1 prepared in Example 1 and heating to 70 ° C. in a nitrogen atmosphere, a mixed solution having the following composition was gradually added dropwise while stirring with a motor, and polymerization was performed. Went. The mixture used consisted of 4.5 parts benzyl methacrylate, 1.2 parts butyl acrylate, 0.3 parts acrylic acid, 0.07 parts potassium hydroxide, 0.05 parts potassium persulfate and 20 parts water. After the polymerization for 5 hours as described above, purification was performed by centrifugation in the same manner as in Example 1 to obtain a dispersible colorant 7. The mixture was mixed so as to have the composition shown in the following table, and further filtered under pressure through a membrane filter having a pore size of 2.5 microns to prepare a recording ink 7 of this example.

[Characteristics of dispersible colorants]
The dispersible color materials obtained in Examples 1 to 7 above were observed and measured for various physical properties by the methods described below, and the results obtained are shown in Table 2.

<Adhesion / spotting of resin fine particles>
Each dispersible colorant is dispersed in water and dried, and observed with a scanning electron microscope JSM-6700 (manufactured by JEOL Hitec Co., Ltd.) at a magnification of 50,000 times, and the resin fine particles are fixed to the colorant. The properties of the fixed resin fine particles were evaluated as follows.
(Adhesive state of resin fine particles)
○: It was confirmed that resin fine particles were fixed.
X: It was not possible to confirm that the resin fine particles were fixed.
(Dispersion of resin fine particles)
○: At the time of observation, it was confirmed that resin fine particles were scattered.
X: At the time of observation, it was observed that the resin fine particles were localized or fixed non-uniformly.

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

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

[Evaluation method and evaluation result of ink composition]
Using each recording ink obtained by the above-described method, the ink characteristics were evaluated as follows. Further, printing on a recording medium was performed with an inkjet recording apparatus, and the obtained images were evaluated. An image is formed using BJ S600 marketed by Canon Inc. as an ink jet recording apparatus, and the optical density (OD) of printed printed matter, scratch resistance, marker resistance, The long-term storage stability of the ink composition was evaluated as follows, and the results are shown in Table 3.

<Uniformity>
In order to produce the ink, the ink jet printer BJ S600 is allowed to stand for 1 hour or more in a temperature of 15 ° C. and a humidity of 10% RH. After that, an ink droplet is ejected from a nozzle, and the nozzle is not used for 20 seconds. The degree of ejection stability when one ink droplet was ejected was visually evaluated according to the following criteria.
A: Normal printing can be performed.
B: Although there is a slight disturbance in printing, it is at a level where there is no problem in actual use.
C: Non-ejection or printing disorder is significant.

<Discharge stability>
The ejection stability was judged visually by printing 100 sheets of specific Bk text continuously, comparing the initial printed matter with the last printed matter.
A: There is no streak or unevenness, and there is no difference between the initial stage and the final stage.
B: Although there are slight streaks, unevenness and twist, printing can be performed without any problem.
C: Degradation is greatly observed or printing cannot be performed.

<Optical density (OD)>
After printing a 5 cm square patch on Canon PPC paper using each recording ink, the optical density (OD) of the printed matter after one day was measured and evaluated according to the following criteria.
A: OD of printed matter is 1.0 or more.
B: OD of printed matter is 0.8 or more and less than 1.0.
C: OD of printed matter is less than 0.8.

<Abrasion resistance>
The scratch resistance of the printed matter was evaluated based on the following criteria by rubbing the printed portion with a Silbon paper having a weight of 40 g / cm ² 5 times, visually observing the disorder of the printed portion.
A: There is no disorder of printing due to rubbing or smearing of the white part.
B: There is almost no disorder of printing due to rubbing and no smearing of the white part, and it is not worrisome.
C: Printing is greatly disturbed by rubbing, and white portions are stained.

<Marker resistance>
The marker resistance of the printed matter was evaluated based on the following criteria by tracing the printed portion once with a fluorescent yellow marker pen (Zebra Optix) and visually observing the disorder of the printed portion.
A: The printed part is not disturbed.
B: There is little disorder of printing in the traced part, and the pen tip is hardly soiled.
C: The trace of the traced part is greatly disturbed, and the pen tip is colored.

<Long-term storage stability>
Storage stability was determined by visual observation of the dispersion state in the ink after placing each ink composition in a glass sample bottle and leaving it in that state for one month at room temperature. The evaluation criteria are as follows.
A: No aggregation or sedimentation of solid content is observed.
B: Sedimentation of solid content is slightly observed, but when shaken lightly, it returns to the original uniform dispersion state. C: Aggregation / sedimentation of solid content is observed, and even if lightly shaken, it does not become uniform.

  Dispersible colorants 1 to 7 having the characteristics shown in Table 2 were obtained in Examples 1 to 7. Further, as shown in Table 3, all the recording inks showed excellent printing performance.

[Examples 8 to 14]
The recording inks according to Examples 8 to 14 were mixed so as to have the component compositions shown in Table 4 below, and further filtered under pressure through a membrane filter having a pore size of 2.5 microns.

[Physical properties and evaluation of each recording ink]
Regarding the recording inks 8 to 14, the same items as those in Examples 1 to 7 were evaluated for printing. Furthermore, in Examples 8 to 14, the following evaluation regarding quick drying was additionally performed.

<Quick-drying>
One minute after the completion of printing, the printed portion was rubbed with a finger, and the printed portion was evaluated for stains according to the following criteria.
A: There is almost no stain on the white paper portion.
B: The blank paper portion is slightly stained, but there is no problem in character recognition.
C: Disturbance of printing occurs and the blank paper portion is clearly stained.
The results are shown in Table 5. In any of the examples, good discharge characteristics and printing performance were shown, but in Example 13 in which the addition amount of the silicon-based surfactant was large, the discharge stability was inferior to that of the other examples. In Example 14 where the addition amount of the system surfactant was small, the effect of improving the light-emitting property was slightly small. Furthermore, Example 13 was slightly inferior to other examples even in quick-drying, but this is considered to be due to the dispersible colorant 6 used being inferior in the dotted nature of the resin pseudo fine particles. .

[Comparative example]
Comparative Examples 1 to 6 were mixed so as to have the composition shown in Table 6 below, and further prepared by pressure filtration with a membrane filter having a pore size of 2.5 microns, which was the same as in Examples 1 to 7. The printing evaluation was performed on the items.
The results are shown in Table 7. In Comparative Examples 1 to 4 using only the dispersible color material, sufficient firing characteristics were not obtained. In Comparative Examples 5 and 6 composed of a silicone-based surfactant and a pigment dispersion formed by resin dispersion, not only the discharge characteristics but also the ejection stability and printing characteristics were insufficient.

Furthermore, the following evaluation was additionally performed with respect to Examples 2 to 5 and 9 to 12. <Normal paper color uniformity>
The 5 cm square patches printed with each recording ink were visually evaluated according to the following criteria.
A: The color of the printed part is extremely uniform.
B: There is a part that is partially whitened, but the other parts are almost uniform.
C: Color shade is felt.

<Clogging resistance>
Inkjet printer BJ S600 is left for 1 hour or more in a temperature of 35 ° C. and a humidity of 10% RH. After printing is performed, the nozzle is not used, and after one week, the printer recovers again. The degree of ejection stability when printing was visually evaluated based on the following criteria, and the results are shown in Table 8. A: Normal printing can be performed.
B: Although there is a slight disturbance in printing, it is at a level where there is no problem in actual use.
C: Non-ejection or printing disorder is significant.

  The results are shown in Table 8. In contrast to Examples 2 and 3, Examples 9 and 10 using urea or ethylene urea gave good results in clogging resistance. In contrast to Example 4, Example 11 using 2-pyrrolidone is a plain paper color uniformity and optical density O.D. D. The result was good. In contrast to Example 5, Example 12 using ethylene urea and N-methyl-2-pyrrolidone greatly improved all of the plain paper color uniformity, clogging resistance, and optical density.

  According to the present invention, there is provided an ink composition that has high dispersion stability, is free from detachment of a resin component from a coloring material, is stable for a long period of time, and is particularly excellent in light emission and good printing performance. Is done. Furthermore, as another effect of the present invention, an ink tank, an ink jet recording apparatus, an ink jet recording method, and an ink jet recorded image using such an excellent ink composition are provided.

  As another effect of the present invention, an ink composition excellent in plain paper color uniformity is provided, and as another effect, an ink composition excellent in clogging resistance is provided. Another effect of the present invention is to provide an ink composition that gives a printed matter with a high print density on plain paper.

It is a schematic diagram which shows the basic structure of the dispersible color material which has fixed the chargeable resin pseudo fine particles by this invention. It is a schematic diagram of the typical process in the manufacturing method of this invention.

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

Claims (12)

  An ink composition comprising at least a dispersible color material, water, a water-soluble organic solvent, and a silicon-based surfactant. The dispersible color material is a color material and a chargeable resin smaller than the color material. An ink composition comprising a dispersible color material having pseudo fine particles and having the color material and the chargeable resin pseudo fine particles fixed to each other.   The ink composition according to claim 1, wherein a plurality of the chargeable resin pseudo fine particles are scattered and fixed to the color material.   The ink composition according to claim 1, further comprising an acetylene glycol surfactant.   The ink composition according to any one of claims 1 to 3, wherein the solubility of the silicon surfactant in water is 0.5 mass% or more.   The ink composition according to claim 1, further comprising a urea derivative as a wetting agent.   The ink composition according to any one of claims 1 to 5, further comprising at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. object.   The ink composition according to any one of claims 1 to 6, wherein a content of the silicon surfactant is 0.005 mass% or more and less than 2 mass%.   The ink composition according to claim 1, wherein the color material is a pigment.   An ink tank comprising the ink composition according to any one of claims 1 to 8.   An ink jet recording apparatus comprising the ink composition according to any one of claims 1 to 8.   An ink jet recording method comprising: forming an image with an ink jet recording apparatus using the ink composition according to claim 1. An ink jet recording image formed by an ink jet recording apparatus using the ink composition according to any one of claims 1 to 8.

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