JP2006008907A - Aqueous inkjet recording ink, inkjet recording device and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous inkjet recording ink which gives an image attaining excellent image qualities and fastness (particularly light resistance) particularly in the case of a thin ink and gives an image excellent in scratch resistance even on a recording paper. <P>SOLUTION: The aqueous inkjet recording ink comprises a dispersible coloring material, comprised of a water-insoluble coloring material and at least one fine pseudoparticle of a chargeable resin, and a water-soluble resin, where the dispersible coloring material is solely dispersed by causing the fine pseudoparticle of the chargeable resin to adhere to the water-insoluble coloring material, the concentration of the water-insoluble coloring material in the ink being at most 1 mass% based on the whole mass of the ink, and the ratio (Ba/P ratio) of the total mass (Ba) of the resin component in the ink to the mass (P) of the water-insoluble coloring material in the ink is larger than 1. The inkjet recording device, the recording method and the recorded image are also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  The ink jet recording method is a method for recording images, characters, etc. by ejecting micro droplets of ink from nozzles to reach a recording medium (paper, etc.) based on various operating principles. Are easy to use, have high flexibility in recording patterns, and do not require development and fixing operations, and are rapidly spreading in various applications. In particular, in recent years, full-color water-based inkjet recording technology has made remarkable progress, and it is possible to form multicolored images that are comparable to multicolored printing by conventional platemaking methods and printing by color photographic methods. It is possible. In addition, when the number of copies is small, a printed matter can be obtained at a lower cost than ordinary multicolor printing or printing. Therefore, the ink jet recording method is being widely applied to the field of full color image recording.

  In response to demands for further improvement in recording characteristics such as higher recording speed, higher definition, and full color, improvements in aqueous inkjet recording apparatuses and recording methods have been made. As a trend in recent years, in order to obtain a better ink jet image, not only the water material that is essentially insoluble in water is stably dispersed in the ink, but also the obtained printed matter has excellent image quality and excellent quality. There is a demand for achieving both scratch resistance.

  In order to use a color material insoluble in water, particularly a pigment, as a color material component of an aqueous inkjet recording ink, it is necessary to stably disperse the color material in water. When a water-insoluble colorant is used as an aqueous inkjet recording ink, it is generally performed to stabilize the dispersion using a surfactant or a polymer dispersant (also referred to as a dispersion resin). Since the dispersion resin has a high affinity for water, there is a problem that the dispersion resin is easily detached from the surface of the coloring material and sufficient dispersion stability cannot be maintained in the long term.

  On the other hand, a method of chemically modifying the surface of the water-insoluble colorant has been studied so that it can be stably dispersed without containing a dispersion resin or a surfactant. For example, “in an aqueous colored fine particle dispersion containing a water-insoluble colorant, the colored fine particle dispersion was polymerized by adding a vinyl monomer after dispersing the water-insoluble colorant in an aqueous medium in the presence of the dispersant. And exhibiting dispersion stability when the water-insoluble colorant is dispersed, and poor stability of the latex produced when the vinyl monomer is polymerized in the presence of the dispersant alone. There is a proposal for “a water-based colored fine particle dispersion characterized by this” (see Patent Document 1), and it is said that an ink for inkjet recording excellent in dispersion stability and the like was obtained by using the dispersion.

JP 2003-34770 A

  However, as a result of further investigation by the present inventors on the above-described prior art, the ink obtained by the above technique cannot obtain an image having a sufficient print density, particularly on plain paper, depending on the recording medium used for image formation. It was found that there was a clear difference in print density between glossy paper and plain paper. This is because, in the above-described technique, the dispersion of the dispersant from the surface of the pigment hardly occurs and the polymerization progressed on the surface of the pigment to which the dispersant was adsorbed. This is because the dispersant acts as a penetrant, particularly on plain paper.

  Therefore, it is difficult to obtain a printed matter that has both excellent image quality and excellent fastness when a coloring material that is essentially insoluble in water is stably dispersed in the ink and used as an ink for inkjet recording. At present, there is no known ink that can achieve all these requirements in good condition. In particular, in the case of “light ink” having a low color material density, it is more difficult to satisfy the light resistance of the image than in the case of normal ink. In the present invention, an ink having a color material concentration of 1% by mass or less with respect to the total mass of the ink is referred to as “light ink”.

  Therefore, the object of the present invention is to solve these problems of the prior art, and in particular, in a light ink, an image obtained can achieve excellent image quality and fastness (especially, light fastness). An object of the present invention is to provide a water-based inkjet recording ink capable of obtaining an image excellent in scratch resistance even on recording paper. Furthermore, another object of the present invention is to provide an excellent ink jet recording apparatus, an ink jet recording method, and an ink jet recorded image capable of obtaining a printed matter having both excellent image quality and excellent fastness.

  As a result of intensive studies to solve the above-described problems of the prior art, the inventors have been able to maintain high dispersion stability essentially without the need for surfactants or polymer dispersants, and for recording. When applied on paper, a new dispersible colorant having sufficient adhesiveness or film-forming property is used, and further, a water-soluble resin is used in combination, which is sufficient for inkjet recording applications while being a dispersible colorant. A water-based inkjet recording ink is obtained that has excellent ejection stability and dispersion stability, and is capable of giving printed matter with high image quality and excellent fastness (especially light resistance) while being a light ink. As a result, the present invention has been found.

The above object is achieved by the present invention described below.
1. A water-based inkjet recording ink comprising a water-insoluble colorant and a dispersible colorant composed of one or more kinds of chargeable resin pseudo fine particles and a water-soluble resin, wherein the dispersible colorant is the water-insoluble colorant. Are dispersed alone by fixing the chargeable resin pseudo fine particles, and the concentration of the water-insoluble colorant in the ink is 1% by mass or less of the total mass of the ink, and the resin content in the ink is A water-based inkjet recording ink, wherein the ratio (Ba / P ratio) of the total mass (Ba) to the mass (P) of the water-insoluble colorant in the ink is greater than 1.
2. A water-based inkjet recording ink comprising a water-insoluble colorant and a dispersible colorant composed of one or more kinds of chargeable resin pseudo fine particles and a water-soluble resin, wherein the dispersible colorant is the water-insoluble colorant. Are dispersed alone by being scattered and fixed with the above-mentioned chargeable resin pseudo fine particles, and the concentration of the water-insoluble colorant in the ink is 1% by mass or less of the total mass of the ink, and the ink A water-based inkjet recording ink, wherein the ratio (Ba / P ratio) of the total mass (Ba) of the resin content in the ink to the mass (P) of the water-insoluble colorant in the ink is greater than 1.

3. The water-based inkjet recording ink according to 1 or 2, wherein the chargeable resin pseudo fine particles have a polar group.
4). 4. The aqueous inkjet recording ink according to 3, wherein the polar group is an anionic group or a cationic group.
5. The water-based inkjet recording ink 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 water-based inkjet recording ink according to any one of 1 to 5, wherein the dispersible colorant has a surface energy of 70 mJ / m ² or less.

7). In any one of 1 to 7, wherein the charged resin pseudo fine particles include a copolymer component synthesized from a monomer component including at least one hydrophobic monomer and at least one hydrophilic monomer. The water-based inkjet recording ink described.
8). 8. The water-based inkjet recording ink according to 7, wherein the copolymer component has a glass transition temperature of −60 ° C. or higher and 120 ° C. or lower.
9. The aqueous inkjet recording ink according to 7 or 8, wherein the hydrophobic monomer contains at least a monomer having a methyl group at the α-position and having a radical polymerizable unsaturated double bond.
10. The aqueous inkjet recording ink according to any one of 7 to 9, wherein the hydrophobic monomer contains at least a (meth) acrylic acid ester compound.
11. 11. The aqueous inkjet recording ink according to 10, wherein the hydrophobic monomer contains at least one selected from benzyl methacrylate or methyl methacrylate.
12 The aqueous inkjet recording ink according to any one of 7 to 11, wherein the hydrophilic monomer contains at least an anionic monomer.
13. 13. The aqueous inkjet recording ink according to 12, wherein the anionic monomer includes at least one selected from acrylic acid, methacrylic acid, p-styrenesulfonic acid, and salts thereof.
14 The water-soluble resin comprises a copolymer component synthesized from a monomer component containing at least one hydrophobic monomer and at least one hydrophilic monomer, and the hydrophilic monomer is an anionic monomer. 14. The water-based inkjet recording ink according to any one of 1 to 13, which contains at least
15. 15. The water-based inkjet recording ink according to 14, wherein the anionic monomer includes at least one selected from acrylic acid and methacrylic acid.

16. An ink jet recording apparatus in which an ink is applied onto a recording medium by an ink jet recording method, and the ink is the ink for ink jet recording according to any one of 1 to 15, wherein the ink is an ink jet recording. apparatus.
17. An ink jet recording method for forming an image by applying ink onto a recording medium by an ink jet recording method, wherein the ink for ink jet recording according to any one of 1 to 15 is used as the ink. .
18. An ink jet recording image, wherein the ink is an ink for ink jet recording according to any one of 1 to 15, in an ink jet recording image formed by applying ink on a recording medium by an ink jet recording method.

  A novel composition that can maintain high dispersion stability in ink without essentially requiring a surfactant or a polymer dispersant, and has sufficient adhesiveness or film-forming property when applied on recording paper. In addition, the dispersible colorant and the water-soluble resin are used together in a state where the ratio of the total resin mass to the mass of the water-insoluble colorant in the ink is greater than 1. According to the configuration of the present invention, although it is a dispersible color material, it has sufficient ejection stability and dispersion stability for ink jet recording applications, and yet it is a light ink, while having high image quality and excellent fastness (especially, There is provided an aqueous inkjet recording ink (hereinafter referred to as ink) from which a printed matter having light resistance can be obtained. In addition, according to the present invention, an excellent ink jet recording method, ink jet recording apparatus, and ink jet recorded image capable of obtaining the above effects are provided.

  Hereinafter, the present invention will be specifically described with reference to preferred embodiments. A first feature of the present invention is that the ink includes a dispersible color material composed of a water-insoluble color material (hereinafter also referred to as a color material) and a chargeable resin pseudo fine particle, and the water-insoluble color material is a chargeable resin pseudo fine particle. It is in the point which has adhered.

  FIG. 1 shows a schematic diagram of a dispersible color material in which chargeable resin pseudo fine particles 2 are fixed to a water-insoluble color material 1 that characterizes the present invention. 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.

  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 colorant has excellent adhesion when applied to a recording medium due to the presence of a resin component adhering to the 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. Since the pseudo fine particles are not detached from the surface of the color material, they are 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, and the resin aggregates are in the form of fine particles. Or it has a stable form as a micro-aggregate close to it. Details of the chargeable resin pseudo fine particles will be described later.

  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 been achieved. FIG. 4 shows a schematic diagram in which the interface between the chargeable resin pseudo fine particles and the color material is enlarged. First, at the interface with the coloring material, the chargeable resin pseudo fine particles are formed by entangled with polymers composed of various monomer unit compositions (indicated by 9-1 and 9-2 in the figure). At this time, the polymer has various structures locally, and the surface energy state is distributed. Two interfaces 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) 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 shown in FIG. It is expected that the fixed state of the present invention is established by the interaction.

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

  In addition, as a merit of the dispersible colorant of the present invention fixing the charged resin pseudo fine particles, the specific surface area of the dispersible colorant increases depending on the form, and the chargeable resin pseudo fine particles are on the surface in many parts. The point which can distribute the electric charge which has is mentioned. 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 form of the dispersible color material of the present invention is a form in which more surface charges are more efficiently arranged on the surface of the dispersible color material. High dispersion stability can be imparted even when the substantial acid value or amine value of the resin component is smaller than the form coated with.

  In the present invention, the state in which the coloring material “fixes” the resin fine particles can be simply confirmed by the following method. The ink or water dispersion in which the color material is dispersed is first separated in a centrifuge at 12,000 rpm for 60 minutes. Of the separated substances, the lower layer sediment containing the color material is redispersed in pure water and dried. The ratio of the color material to the resin (resin mass / color material mass, B / C Measured) (B / C-1).

  Subsequently, the re-dispersion of the sediment in the first separation in pure water is subjected to a second separation under the conditions of 80,000 rotations and 90 minutes, and the lower layer sediment containing the coloring material is washed with water. Then, the B / C is measured again on the dried product (B / C-2). And ratio (B / C-2) / (B / C-1) of the ratio of the coloring material and the resin with respect to the dried product measured in each of the above steps is in the range of 0.5 to 1.0. In this case, it is determined that the color material and the resin are fixed.

  Further, in addition to the above, the sediment in the first separation and the sediment in the second separation are each redispersed in water, dried, and observed with a scanning electron microscope at 50,000 times. The color material observed at that time was confirmed to have a plurality of resin fine particles adhering to the surface, and the respective precipitates from the first separation and the second separation had the same form. If this is the case, it is determined that the coloring material has the resin fine particles fixed thereto.

  When the above operation is applied to a dispersible color material other than the dispersible color material used in the present invention, the value of (B / C-2) / (B / C-1) is even smaller than 0.5. Value. In addition, even when (B / C-2) / (B / C-1) is in the range of 0.5 to 1.0, if the color material is not resin fine particles, In particular, the sediment from the second separation is observed as an image in which the color material is irregularly encapsulated in the resin, or as an image in which the color material is not clearly defined, and adheres to the color material in a regular structure as resin fine particles. Is not observed.

  The above-mentioned B / C value can be generally obtained by a differential thermogravimetry, but in the present invention, a value measured and calculated by TGA / SDTA851 manufactured by METTTLER was used. The value of B / C is determined by drying a re-dispersed precipitate obtained by the above-described first or second separation in water, weighing it, and using a differential thermogravimetric apparatus, using a nitrogen atmosphere, or It is calculated by determining the mass change before and after the decomposition temperature of the coloring material and the resin component when the temperature is raised in the atmosphere.

  In the present invention, “singlely dispersed” means “the water-insoluble colorant can be stably dispersed in water and water-based inks without the aid of other surfactants or polymer dispersants”. Means state. This definition and determination method will be described in detail later. The black ink used in the present invention is the above-described specific one, and includes a surfactant and / or a polymer dispersant that prevents aggregation of the color material and accelerates ink penetration when landed on the recording paper. It is not necessary to contain it, or it is suppressed to a very small amount so as to optimize the penetration of the ink. Further, the black ink used in the present invention is due to an increase in ink viscosity, which has been a problem with ink jet recording inks containing a polymer dispersant, and because the polymer dispersant sticks to the vicinity of the discharge port of the ink jet recording apparatus. Generation | occurrence | production of the shift | offset | difference of a discharge direction, etc. was suppressed.

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

  As a preferred embodiment of the ink according to the present invention, it is desirable that the charged resin pseudo fine particles described above have a polar group. When the resin fine particles have a polar group as described above, high dispersion stability can be imparted to the water-insoluble colorant. The polar group may be an anionic group or a cationic group. The water-insoluble colorant to which the charged resin pseudo fine particles having an anionic group or a cationic group are fixed has a high specific surface area due to its form, and further has a large number of polar groups on the surface. Accordingly, by fixing the chargeable resin pseudo fine particles having a polar group to the water-insoluble colorant, the water-insoluble colorant becomes a dispersible colorant that is dispersed and stabilized in a state having a high surface potential. As a result, it is possible to improve the dispersion stability and storage stability of the ink containing the dispersible color material.

  When the ink according to the present invention is in the above-described form, the water-insoluble colorant has many polar groups on a high specific surface area by fixing the chargeable resin pseudo fine particles, and has better storage stability. Realized. Accordingly, more preferable results can be obtained when the chargeable resin pseudo fine particles are in a state of being scattered and fixed to the water-insoluble colorant. In particular, when the charged resin pseudo fine particles having a polar group are fixed, there is a certain distance between the fixed charged resin pseudo fine particles, and preferably a part of the surface of the water-insoluble colorant is exposed. It is desirable that The form of such a dispersible colorant can be confirmed by observing with a transmission electron microscope or a scanning electron microscope. It is possible to observe a state in which a plurality of resin 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 resin fine particles and the resin fine particles. . Although the resin fine particles are partially close and may be observed in some cases, there may be a distance between the resin fine particles as a whole, and there are portions where the color material surface is exposed, and It will be apparent to those skilled in the art that when these states are distributed, the resin fine particles are considered to be scattered and fixed to the water-insoluble colorant.

  Furthermore, the ink according to the present invention exhibits excellent quick drying on the recording medium depending on the form of the dispersible color material in which the water-insoluble color material described above has the charged resin pseudo fine particles fixed to the surface. It became clear. The reason for this is not clear, but is thought to be based on the following mechanism. As described above, the water-insoluble color material is dispersed in the ink in a state where the chargeable resin pseudo fine particles are fixed to the color material surface. When this ink reaches the recording medium, the ink solvent becomes pores on the recording medium due to capillarity (in the case of plain paper, voids between cellulose fibers; in the case of coated paper and glossy paper, the pores of the receiving layer). Is absorbed). At this time, because of the morphological features of the color material described above, resin fine particles are scattered at portions where the color materials are in contact with each other, so that many fine gaps are formed, and the ink solvent existing between the color materials has a capillary phenomenon. Work. For this reason, the ink solvent between the color materials is quickly absorbed into the recording medium. In the ink according to the present invention, the quick-drying property is expected to be achieved by the above-described mechanism because the ink-dispersed pseudo fine particles are more preferably quick-drying.

  When the charged resin pseudo fine particles have a polar group, the surface functional group density of the water-insoluble colorant to which the resin fine particles are fixed is preferably 250 μmol / g or more and less than 1,000 μmol / g, and more preferably 290 μmol / g. It is preferably at least 900 μmol / g. When the surface functional group density is smaller than this range, the long-term storage stability of the dispersible colorant is deteriorated, the cohesive force on the recording medium is insufficient, and the image formed on the recording medium is poorly scratched. It may become a thing. In addition, when the surface functional group density is considerably larger than this range, the dispersion stability of the dispersible color material in the ink becomes too high, and the color material is likely to permeate on the recording medium, ensuring a high print density. May be difficult to do. In particular, in the ink according to the present invention, when carbon black is used as the water-insoluble colorant, it is necessary to increase the storage stability because of the high specific gravity of the carbon black, and the black density on the recording medium is particularly high. More preferably, it is set at 350 μmol / g or more and less than 800 μmol / g.

  In particular, when the chargeable resin pseudo fine particles have an anionic group as a polar group, the surface functional group density in the above is obtained, for example, as follows. A large excess amount of an aqueous hydrochloric acid solution is added to the aqueous dispersion or ink containing the dispersible colorant, and the mixture is precipitated in a centrifuge at 20,000 rpm for 1 hour. The sediment is collected, redispersed in pure water, and the solid content is measured by a drying method. The redispersed sediment is weighed, and a dispersion obtained by adding a known amount of sodium hydrogen carbonate and stirring the mixture is further sedimented in a centrifuge at 80,000 rpm for 2 hours. The supernatant is weighed, and is obtained as the number of moles per gram of pigment by subtracting the known amount of sodium hydrogencarbonate from the neutralized amount obtained by neutralization titration with 0.1 N hydrochloric acid. In the case of having a cationic group as a polar group, it can be determined by using the same method using sodium hydroxide instead of hydrochloric acid and ammonium chloride instead of sodium hydrogen carbonate.

It is also a preferred embodiment that the surface energy of the dispersible color material composed of the water-insoluble color material to which the chargeable resin pseudo fine particles are fixed is 70 mJ / m ² or less. According to the study by the present inventors, by controlling the surface energy of the dispersible color material in a range of 70 mJ / m ² or less, achievement of excellent dispersion stability in the ink of the dispersible color material, Appropriate fixability on the recording medium can be obtained. On the other hand, when the surface energy of the dispersible color material is remarkably larger than 70 mJ / m ² , the hydrophilicity of the color material surface is too high, so that the color material and the water-based ink medium are separated on the recording medium. May not work, and the print surface may dry slowly. In addition, although the storage stability of the ink is excellent, the water resistance of the printed matter may be insufficient. This is because the hydrophilicity of the color material surface is too high, and when the printed matter is exposed to water or an aqueous marker pen, the color material aggregated on the paper surface is redispersed due to the strong hydrophilicity of the color material surface. It is thought to be caused by this. The surface energy of the dispersible colorant used in the present invention is determined from any of the surface charge and functional group structure of the water-insoluble colorant used, and the chemical structure and surface structure of the chargeable resin pseudo fine particles fixed to the colorant. The chemical structure and surface structure of the chargeable resin pseudo fine particles can be controlled from either the residue of the polymerization initiator used during the resin fine particle synthesis or the constituent monomer components.

  As used herein, “surface energy” refers to the free energy at the interface of a substance and depends on the chemical structure of the interface. The higher the surface energy, the easier it gets wet and the higher the affinity with water. In the present invention, a value obtained using an inverse gas chromatograph marketed by Surface Measurement System is defined as the surface energy value of the dispersible colorant. Specifically, it is obtained by extrapolating from the retention time of each gas when a dispersible colorant is dried to form a powder as a stationary phase and an organic gas having a different polarity as a mobile phase.

  Further, when the surface zeta potential in the aqueous medium constituting the ink of the dispersible colorant composed of the water-insoluble colorant to which the chargeable resin pseudo fine particles are fixed has an anionic group as a polar group, an average value is obtained. It is also a preferred embodiment that the average value is in the range of +10 to +60 mV in the case of having a cationic group in the range of -20 to -80 mV. By setting it as the above range, excellent long-term storage stability can be imparted to the ink. On the other hand, when the zeta potential is in the range of −15 mV to +10 mV, the long-term storage stability of the 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.

  As used in this specification, the “zeta (ζ) potential” is also called a zeta potential or an electrokinetic potential, and means a potential difference generated at the interface between a solid and a liquid that are in contact with each other when they are in relative motion. To do. Used for analysis of the surface state of solids present in the liquid. Of the electric double layer generated at the interface between the solid and liquid, there is a stationary phase (or adsorbed phase) in the part close to the solid, opposite to the solid surface. Charge ions are fixed. Since the stationary phase moves with the solid when the solid and the liquid move relative to each other, the potential difference that actually controls the motion is considered to be the potential difference between the surface of the stationary phase and the inside of the solution. Is called the zeta potential. The zeta potential takes a positive or negative value depending on whether the charge of the stationary phase is positive or negative. 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. The zeta potential is an important physical property value in the dispersion stability and storage stability of the ink for ink jet recording.

  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 A hetero-aggregation phenomenon is known, in which an attractive force acts between the surfaces of the dispersion, which facilitates aggregation.

  That is, also in the ink according to the present invention, the absolute value of the zeta potential of the water-insoluble colorant is uniform, so that an effect on dispersion stability is exhibited. According to the present inventors, it has become clear that desirable dispersion stability can be obtained if the zeta potential of the dispersible colorant used in the present invention is within 50 standard deviations from the average value. However, the zeta potential is a value that varies depending on various conditions such as the dielectric constant, pH, and salt concentration of the aqueous medium in which the coloring material (the same applies to all other colloidal dispersions) is dispersed. The absolute value and distribution measured in the medium conditions should be discussed.

  The zeta potential of the water-insoluble colorant in the water-based ink can be measured by a generally known method. In the present invention, ZEECOM manufactured by Microtech Nichion Co., Ltd. is used, and the water-based mixing used in the ink An image processing method is used to measure the moving speed of dispersed particles (that is, a dispersible color material in the present invention) when a water-insoluble color material to be measured is diluted to an appropriate magnification in a solvent and a constant electric field is applied. The value obtained by measuring at However, particularly in the case of an ink containing a large amount of a specific electrolyte, if the above-described measurement is performed in an aqueous mixed solvent having the same configuration, the electrical conductivity of the solvent may become abnormally high and may not be measured. In this case, the zeta potential of the water-insoluble colorant in the ink medium can be known by removing or reducing the electrolyte component and measuring the pH of the medium in accordance with the pH when the ink is used. In this case, since a lot of electrolyte is contained in the actual ink, the storage stability of the ink generally tends to be inferior. However, more preferable storage stability is achieved by setting the zeta potential within the range preferably used in the present invention. It can be set as the ink which has property.

  As shown in FIG. 1, the ink according to the present invention is present in the ink in a state where the chargeable resin pseudo fine particles 2 are fixed to the surface of the water-insoluble colorant 1. Therefore, the color material adheres to the recording paper and the adjacent color material on the recording medium via the resin fine particles fixed to the surface.

  Therefore, the printed matter obtained using the ink according to the present invention has excellent scratch resistance and marker resistance. As a more preferred embodiment, by using the ink in which the charged resin pseudo fine particles are further dispersed, it is possible to perform high gloss printing on a glossy recording medium, which is usually difficult with an ink using a water-insoluble colorant. Become. More preferably, in the state where the charged resin pseudo fine particles (A) fixed to the water-insoluble colorant and the charged resin pseudo fine particles (B) dispersed in the ink are present, the resin fine particles (A ) And the monomer component constituting the resin fine particles (B) include one or more common monomer components, so that the water-insoluble colorant to which the resin fine particles (A) are fixed, Since the affinity with the resin fine particles (B) is increased and the adhesive force is increased, the scratch resistance of the printed matter particularly on the glossy recording medium is greatly improved.

[Color material]
The water-insoluble colorant that is an essential component of the ink according to the present invention will be described. The water-insoluble colorant used in the present invention is a water-insoluble colorant such as a hydrophobic dye, an inorganic pigment, an organic pigment, a metal colloid, or a colored resin particle, and can be stably dispersed in water together with a dispersant. Anything can be used. 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. When a color material larger than 0.5 μm is used, there is a high possibility of clogging the discharge port of the ink jet recording apparatus, which is not suitable for printing a finer image. On the other hand, if the color material is significantly smaller than this range, there is a possibility that the weather resistance of the image, which is a merit by using the water-insoluble color material, cannot be sufficiently obtained.

  Examples of the inorganic pigment that can be effectively used as a coloring material in the present invention include carbon black, titanium oxide, zinc white, zinc oxide, lithopone, cadmium red, red rose, molybdenum red, chrome vermilion, 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, 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.

  The present invention is a technique relating to “light ink”, and the concentration of the insoluble color material in the ink according to the present invention is 1% by mass or less of the insoluble color material with respect to the total amount of the ink. Ink jet recording ink having a color material amount of 1% by mass or less with respect to the total amount of ink gives an image having the same hue on a recording medium. Often used in ink jet recording in combination with (dark ink). In this way, by using the light ink together with the dark ink, it is possible to form a silver salt photographic-like ink jet recorded image having a very smooth gradation and having no noticeable dot outline. However, the ink according to the present invention is not necessarily used only in combination with the dark ink, and can of course be used alone.

  The more preferable density of the color material constituting the ink according to the present invention is the type of the color material to be used, or the balance with the dark ink when used as an ink set in which the dark ink and the light ink are combined as described above. The density of the color material is preferably 0.9% by mass or less, more preferably 0.8% by mass in consideration of the original purpose of the light ink in which the outline in units of one dot cannot be visually observed. It is as follows. On the other hand, the lower limit of the water-insoluble colorant concentration is 0.1% by mass or more, particularly 0.2% by mass or more, more particularly 0.2% by mass or more based on the total mass of the ink so that the coloring power as the ink is not too low. It is preferable to set it as 0.3 mass% or more.

[Charged resin pseudo fine particles]
As the chargeable resin pseudo fine particles used in the ink according to the present invention, resin fine particles that are insoluble in water and composed of any commonly used resin component can be used. As for whether it is a chargeable resin pseudo fine particle, it can be self-dispersed in an aqueous medium, and its dispersed particle size in water can be measured by, for example, a light scattering method, preferably the center value of the dispersed particle size Is preferably in the range of 10 to 200 nm. Furthermore, from the viewpoint of long-term storage stability of the ink for inkjet recording, it is more preferable that the polydispersity index of the dispersed particle diameter is suppressed to less than 0.2. If the center value of the dispersed particle diameter is larger than 200 nm or the polydispersity index is larger than 0.2, the original purpose of finely dispersing and stabilizing the water-insoluble colorant may not be sufficiently achieved. When the center value of the dispersed particle diameter is smaller than 10 nm, the form of the resin fine particles cannot be sufficiently maintained, and the resin is easily dissolved in water, so that the merit of the present invention may not be obtained.

  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 viewpoint that it can be generally used and the functional design of resin fine particles can be easily performed, a polymer of a monomer component having a radical polymerizable unsaturated bond, such as an acrylic resin or styrene / acrylic resin, or the like is used. 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. 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 and methacrylic acid.

  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.

  As the nonionic hydrophilic monomer, specifically, for example, monomers having a radical polymerizable unsaturated bond and a hydroxyl group exhibiting strong hydrophilicity in the structure are applicable. Hydroxyethyl (meth) acrylate, hydroxylpropyl (meth) acrylate, and the like are classified into this. In addition, various known or novel oligomers and macromonomers can be used without limitation.

  In particular, the chargeable resin pseudo fine particles are more preferably composed of a copolymer of monomer components containing at least one kind of hydrophobic monomer and at least one kind of hydrophilic monomer, as described above. An ink for ink jet recording having printing characteristics is obtained. That is, when preparing resin fine particles, for example, various types of resin fine particles fixed to the surface of the colorant depending on many control factors such as the type and concentration of the polymerization initiator to be used, the type of monomer to be constituted, and the copolymerization ratio The properties and the like can be appropriately controlled. At this time, at least one kind of good fixing property and heat stability to the water-insoluble colorant can be obtained by using at least one kind of hydrophobic monomer. By using this hydrophilic monomer, good form control and dispersion stability can be imparted, respectively. Therefore, by using these monomers at the same time, it is possible to obtain resin fine particles that are always well fixed to the colorant and have good dispersion stability. In addition to satisfying the above conditions, the resin fine particles fixed to the dispersible colorant and / or the colorant used in the present invention can be selected by appropriately selecting the monomer species and copolymerization ratio constituting the resin fine particles. Additional functionality can be imparted.

  For example, it is also a preferred form that the hydrophobic monomer contains at least a monomer having a methyl group at the α-position and having a radical polymerizable unsaturated double bond. By fixing resin fine particles using a radically polymerizable monomer having a methyl group at the α-position, particularly in a thermal ink jet method in which ink is ejected by thermal energy, the ejectability of an ink for ink jet recording containing a dispersible colorant is improved. Become 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 hydrophobic surface of the water-insoluble colorant, and at the same time, is excellent in copolymerization with the hydrophilic monomer component, From the viewpoint of uniformity of the surface properties and uniform adhesion to the water-insoluble colorant, preferable results are given.

  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 preferred reasons, the above two types of monomers impart preferable heat resistance and transparency to the chargeable resin pseudo fine particles, and the ink containing the water-insoluble color material to which the resin fine particles are fixed is excellent on recording paper. It shows color development.

  As described above, the dispersible color material used in the present invention and the color material are fixed by appropriately selecting the monomer type and copolymerization ratio constituting the resin fine particles such as the hydrophobic monomer and the hydrophilic monomer. Although the properties of the resin fine particles can be controlled, it is also a preferred form to control the glass transition temperature of the copolymer component contained in the chargeable resin pseudo fine particles to be −60 ° C. or higher and 120 ° C. or lower. 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 glass transition temperature of the chargeable resin pseudo fine particles can be measured by a commonly used differential scanning calorimetry. For example, in this invention, the value measured using DSC822e by a METTTLER company is used.

  The dispersible color material comprising a copolymer component having a glass transition temperature of −60 ° C. or more and 120 ° C. or less is a color material adjacent on the recording paper due to the high film forming property imparted to the resin fine particles. And a strong colored film can be formed. Accordingly, not only high scratch resistance can be imparted to the printed matter, but also a printed matter having excellent scratch resistance even on a glossy recording medium that is extremely disadvantageous for scratch resistance. In particular, in the form of ink in which the chargeable resin pseudo fine particles are further dispersed together with the dispersible colorant, a printed matter having excellent glossiness, scratch resistance, and scratch resistance on the glossy recording medium can be obtained. .

  Further, in the case of using a pigment as the water-insoluble colorant, the ratio of the pigment and the chargeable resin pseudo fine particles (resin fine particle mass / pigment mass = B / P) is in the range of 0.3 to 0.9. This is also a desirable embodiment in order to improve the scratch resistance of the printed matter. By setting the B / P ratio to 0.3 or more, it is possible to impart excellent scratch resistance to the printed matter by increasing the adhesion between the color materials and between the color material and the recording medium. In particular, a dispersible color material comprising a water-insoluble color material formed by adhering the chargeable resin pseudo fine particles comprising a copolymer component having a glass transition temperature of −60 ° C. or higher and 120 ° C. or lower as described above. When is used, the film-forming property can be expressed more effectively, resulting in an increase in scratch resistance on glossy paper. When B / P is significantly larger than 0.9, the proportion of the chargeable resin pseudo fine particles that are dispersed in the resin fine particles alone without being fixed to the pigment increases, and the effect of improving the dispersion stability of the coloring material is slightly less. Because it is thought that it will begin to become.

  The above-mentioned B / P can be generally obtained by a differential thermogravimetry, but in the present invention, it is a value measured and calculated by TGA / SDTA851 manufactured by METTTLER. In the present invention, the sediment obtained by centrifuging the ink for ink jet recording of the present invention at 80,000 rpm for 2 hours is dried, weighed, and heated in a nitrogen atmosphere or in the air. Mass changes before and after the respective decomposition temperatures of the pigment and the resin component were determined, and B / P was calculated.

  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, when the ink contains an aqueous solvent other than water and various additives such as penetrants, inorganic and organic salts, and preservatives, an anionic property that works effectively to maintain the long-term storage stability of the ink By including a monomer, it is possible to introduce more anionic groups into the charged resin pseudo fine particles, and it is also effective as a method for controlling the surface functional group density of the colorant to a preferable value as described above. is there. 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.

[Water-soluble resin]
The ink according to the present invention includes a water-soluble resin in addition to the dispersible colorant described above. Unlike the chargeable resin pseudo fine particles that characterize the dispersible colorant, the water-soluble resin is contained in a dissolved form in the ink. As the monomer component constituting the water-soluble resin used in the present invention, those mentioned above in the section of [Charged resin pseudo fine particles] may be used. Furthermore, it is preferable to use a water-soluble resin having a dispersant function having a hydrophilic part and a hydrophobic part obtained from these monomers. By adding such a water-soluble resin having a function as a dispersant, the dispersion stability of the dispersible colorant described above in the ink can be further enhanced.

  The chargeable resin pseudo fine particles described above are insoluble in water, whereas the water-soluble resin has a large proportion of hydrophilic portion and is water-soluble. In the present invention, in particular, it comprises a copolymer component synthesized from a monomer component containing at least one hydrophobic monomer and at least one hydrophilic monomer, and the hydrophilic monomer is anionic. It is preferable to use a water-soluble resin containing at least a monomer.

  Specific examples of water-soluble resins that can be used in the present invention include, for example, styrene, styrene derivatives, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, malein, and the like. Block copolymer or random copolymer consisting of at least two monomers selected from acids, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, etc., salts thereof, etc. Is mentioned.

  More specifically, the hydrophobic monomer is preferably a (meth) acrylic acid ester such as benzyl acrylate, methyl methacrylate, benzyl methacrylate, or the like, and acrylic acid or methacrylic acid is used as the hydrophilic monomer. It is particularly preferable to do this.

  The water-soluble resin obtained as described above may be mixed with the color material component before the production of the dispersible color material, or added to the ink in a form added after the production of the dispersible color material. It may be contained, and may be contained in the ink by any method.

  The ink according to the present invention is characterized in that the ratio (Ba / P ratio) of the total mass (Ba) of the resin in the ink to the mass (P) of the water-insoluble colorant in the ink is greater than 1. To do. As described above, the ink according to the present invention contains the chargeable resin pseudo fine particles constituting the dispersible color material and the water-soluble resin as the resin component. Therefore, the total mass (Ba) of the resin content in the ink of the present invention means the total amount of the content of the water-soluble resin and the content of the chargeable resin pseudo fine particles in the ink. Hereinafter, the total mass of the resin contained in the ink is referred to as the total resin mass. In the present invention, the Ba / P ratio was determined by differential thermogravimetry. Specifically, the ink was dried for 24 hours with a 60 ° C. dryer, and measured and calculated with a TGA / SDTA851 manufactured by METTLER TOLEDO.

  Here, since the ink according to the present invention is a light ink having a water-insoluble colorant concentration of 1% by mass or less as described above, it is assumed that the Ba / P ratio is 1 or less. The resin mass is very small, 1% by mass or less. In the dispersible color material in which the chargeable resin pseudo fine particles used in the present invention are fixed to the color material, wart-like resin fine particles are attached around the water-insoluble color material and the surface is uneven (see FIG. 1), when the amount of the resin is small, it is difficult to completely cover the color material particles and the color material particles with the resin on the printed image. As described above, by selecting the chargeable resin pseudo fine particles including the copolymer component having a glass transition temperature of −40 ° C. or higher and 120 ° C. or lower, the direction of film-forming on the printed image Yes, but not completely covered. As a result, the resulting image may not have sufficient scratch resistance.

  Further, the presence of oxygen in the air is involved in the fading of the image due to light. If the color material is covered with resin, the air is blocked. However, when the total amount of resin in the ink is less than 1% by mass, it is difficult to block the air. For this reason, in a light ink having a small color material concentration of 1% by mass or less, even if a dispersible color material in which chargeable resin pseudo fine particles are fixed to an insoluble color material is used, the Ba / P ratio is small. Then, it is considered that photobleaching is somewhat likely to occur. On the other hand, if the Ba / P ratio is larger than 1, the water-insoluble colorant is almost completely covered with the chargeable resin pseudo fine particles and the water-soluble resin contained in the ink. As a result, the color material is shielded from the air on the recording paper. As a result, the image is less prone to photobleaching, and an image excellent in scratch resistance and light resistance can be obtained.

[Synthesis of charged resin pseudo fine particles and fixation to water-insoluble colorant]
A preferred method for producing a dispersible color material used in the ink according to the present invention will be described. According to the study by the present inventors, the dispersible colorant used in the present invention can be produced very simply by applying the aqueous precipitation polymerization method under the following conditions. That is, first, a water-insoluble colorant is dispersed with a water-soluble resin that functions as a dispersant to obtain an aqueous dispersion of the water-insoluble colorant, and then an aqueous radical polymerization initiator is used in the aqueous dispersion. Thus, the chargeable resin pseudo fine particles are fixed by a step of aqueous precipitation polymerization of the radical polymerizable monomer. The dispersible colorant obtained through this step is composed of a water-insoluble colorant in which the charged resin pseudo fine particles synthesized in the aqueous precipitation polymerization process are firmly fixed in a uniform and scattered state. Excellent dispersion stability. In the water-based 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 water-insoluble colorant, 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, the water-insoluble colorant preferably used in the present invention as mentioned above is dispersed in water with a dispersant to obtain an aqueous dispersion. As the dispersant used in this case, any of a general polymer dispersant and a water-soluble polymer compound can be used such as ionic and nonionic. The dispersant used in the present invention is sufficiently water-soluble and has a hydrophobic portion that serves as an adsorption site for the surface of the colorant fine particles and the radically polymerizable monomer added in the polymerization process, particularly the hydrophobic monomer to the oil droplet interface. What is doing is preferable. More desirably, at least one of the hydrophobic monomers used in the subsequent polymerization step is preferably present as a unit constituting the dispersant.

  The method for producing a water-soluble polymer compound that functions as a dispersant that can be used above is not particularly limited. For example, a monomer having an ionic group and another polymerizable monomer can be used in a non-reactive solvent. It can be produced by reacting in the presence or absence of a catalyst. In particular, it is listed from the viewpoint that both the stability in the dispersion system in the subsequent polymerization step and the promotion of fixing of the water-insoluble resin fine particles formed in the dispersion system to the surface of the water-insoluble colorant are compatible. A styrene / acrylic polymer compound obtained by polymerizing a monomer having an ionic group and a styrene monomer as essential components, or a monomer having an ionic group and a (meth) having 5 or more carbon atoms It is also preferable to use a dispersant selected from ionic group-containing acrylic polymer compounds obtained by polymerizing an acrylate monomer as an essential component. 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 water-insoluble colorant in the subsequent aqueous precipitation polymerization process and maintaining the dispersion stability of the water-insoluble colorant in the polymerization process, In the case of using an anionic dispersant, it is desirable to use one having an acid value of 100 to 250, and in the case of using a cationic dispersant, one having an amine value of 150 to 300. When the acid value and the amine value are smaller than this range, the affinity between the hydrophobic monomer and the dispersant is higher than the affinity between the water-insoluble colorant and the dispersant during the aqueous precipitation polymerization. However, since it becomes easy to remove from the surface of the water-insoluble colorant, the dispersed state may not be maintained. In addition, when the acid value and amine value are larger than these ranges, the excluded volume effect of the dispersant on the surface of the water-insoluble color material and the electrostatic repulsion force become too strong. There is a case where the fixation of the pseudo fine particles is inhibited. When an anionic dispersant is used, 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 water-insoluble colorant.

  In the process of converting the water-insoluble colorant into an aqueous dispersion with a dispersant, the colorant preferably has a dispersed particle diameter in the range of 0.01 to 0.5 μm (10 to 500 nm), particularly preferably 0.03 to 0. Disperse in the range of 3 μm (30 to 300 nm). The dispersed particle size in this process largely reflects the dispersed particle size of the water-insoluble colorant to which the obtained chargeable resin pseudo fine particles are fixed, and as described above, the viewpoint of ink jet suitability and dispersion stability, and the weather resistance of the image. In view of the above, the above range is preferable.

  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 water-insoluble colorant obtained by fixing the chargeable resin pseudo fine particles is larger than the particle size distribution of the aqueous dispersion before the polymerization step shown in FIG. Although it tends to be narrow, it basically depends on the particle size distribution of the aqueous dispersion. It is also important to narrow the particle size distribution of the color material in order to reliably induce fixation due to heteroaggregation of the water-insoluble color material and the resin fine particles. According to the study by the present inventors, in order to obtain good dispersion stability and ejection stability as an ink for ink jet recording, the polydispersity index of the coloring material is in the range of 0.25 or less. It is desirable to use it.

  Here, the particle size of the colorant in a dispersed state varies depending on various measurement methods. In particular, the organic pigment is very small in the case of spherical particles. The particle size and polydispersity index obtained by measuring with the light scattering method as the principle and by 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 can also be used and 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 to 130% by mass with respect to the pigment.

  As another method for dispersing the color material, even when a surfactant is used as a dispersant, the manufacturing methods described in order below can be applied, but in the case where a surfactant is used. May have a stronger adsorbing power to the colorant than the polymer dispersant, and may inhibit the fixing of the chargeable resin pseudo fine particles. In addition, in the case of using a surfactant having a weak adsorptive power to the coloring material, it is necessary to add a large amount of the surfactant in order to sufficiently disperse the coloring material. Inhibits adhesion to color materials. Further, even when a water-insoluble color material having a chargeable resin pseudo fine particle fixed thereto is obtained, when used in an inkjet recording ink, the remaining surfactant induces penetration of the color material into the recording medium, resulting in a high image quality. The concentration cannot be obtained. For the above reasons, it is desirable to use a polymer dispersant when applying the production method of the present invention.

  Further, it is preferable that the water-insoluble colorant used does not have self-dispersibility. When the water-insoluble coloring material itself has self-dispersibility, even when the preferred polymer dispersing agent described in this specification is used, the dispersing agent does not sufficiently adsorb to the coloring material and efficient charging is performed. May not be able to induce fixation of the conductive resin pseudo fine particles.

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

(Radical polymerization initiator)
As the radical polymerization initiator used in the above, any general water-soluble radical polymerization initiator can be used. Specific examples of the water-soluble radical polymerization initiator include persulfate. 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 is selected which gives a polymerization initiator residue having the same sign as the surface characteristics of the water-insoluble colorant to which the chargeable resin pseudo fine particles to be obtained are fixed. That is, for example, when a water-insoluble colorant having an anionic group is obtained, the surface charge can be obtained more efficiently by selecting an initiator residue that is nonionic or anionic. Similarly, when obtaining the said water-insoluble coloring material which has a cationic group, it is preferable to select what makes an initiator residue nonionic or cationic.

(Radically polymerizable monomer)
Since the radical polymerizable monomer used in the above-described production method is a component constituting the above-described chargeable resin pseudo fine particles through the aqueous precipitation polymerization, as described above, the characteristics of the resin fine particles to be obtained and the resin What is necessary is just to select suitably according to the characteristic of the water-insoluble coloring material formed by adhering fine particles. Also in the above production method, any conventionally known radical polymerizable monomer or a radical polymerizable monomer newly developed for the present invention can be used.

(Aqueous precipitation polymerization)
Subsequently, in the case of producing a dispersible colorant characterizing the ink according to the present invention, an aqueous system is a step of fixing the resin fine particles to the particle surface of the water-insoluble colorant while synthesizing the chargeable resin pseudo fine particles. A preferred embodiment of precipitation polymerization is described. FIG. 2 is a process diagram schematically showing a process flow of the manufacturing method. First, as shown in FIG. 2A, an aqueous dispersion in which the colorant 3 is dispersed in the aqueous solution by the dispersant 4 is prepared. Next, the temperature of the dispersion prepared in FIG. 2A is increased while stirring, and the monomer component 6 is added to the dispersion together with, for example, the aqueous radical polymerization initiator 5 (see FIG. 2B).

  The added aqueous radical polymerization initiator 5 cleaves when heated to generate radicals, and among the monomer components added to the aqueous dispersion, a small amount of the hydrophobic monomer dissolved in the aqueous phase and the aqueous phase Contributes to the reaction with the water-soluble monomer. As the reaction proceeds, the oligomers produced by the polymerization reaction of the monomer components become insoluble in water and precipitate from the aqueous phase, but the oligomers precipitated at this time do not have sufficient dispersion stability. Charged resin pseudo fine particles are formed.

  The charged resin pseudo fine particles are further stabilized by heteroaggregating with the water-insoluble colorant 3 dispersed in the aqueous solution as a nucleus. Therefore, the dispersible color material used in the present invention can be obtained as a form in which a plurality of chargeable resin pseudo fine particles are fixed to one color material dispersion unit (see FIG. 2C). Furthermore, in this process, in which precipitation due to polymerization and fixation to the color material proceed simultaneously, the chargeable resin pseudo fine particles cause hetero-aggregation with the color material at a stage where the dispersion stability does not have sufficient dispersion stability. Strong intermolecular force and hydrophobic interaction act between the fine particles and the color material. Furthermore, the chargeable resin pseudo fine particles are adsorbed in a more stable form with respect to the surface shape of the color material, and the color material is strongly Adheres to, ie adheres to Through the above-described process, the dispersible color material having the above-described configuration is easily formed (see FIG. 2D).

  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 to 80 ° C. The reaction time is 1 hour or longer, preferably 6 to 30 hours. The stirring speed during the reaction is 50 to 500 rpm, preferably 150 to 400 rpm.

  In the above-described step, particularly when the charged resin pseudo fine particles are obtained by polymerizing a monomer component containing at least one hydrophobic monomer and at least one hydrophilic monomer, the monomer component is preferably an aqueous radical. It is desirable to drop it into an aqueous dispersion of a water-insoluble colorant containing a 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 chargeable 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 water-insoluble colorant.

  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 an aqueous dispersion of a water-insoluble colorant containing an aqueous radical polymerization initiator, the copolymerization ratio of the hydrophobic monomer and the hydrophilic monomer is always kept constant, and is desired. The chargeable resin pseudo fine particles composed of the 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 an ink jet recording ink using the water-insoluble colorant to which the self-dispersing resin fine particles obtained in the above-described steps are fixed, it is desirable to further perform a purification treatment in addition to the above steps. As a method for purification used at this time, an optimum method 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, the chargeable resin pseudo fine particles made of a desired copolymer can be formed on the surface of the water-insoluble colorant by controlling many control factors. In particular, when an anionic monomer is used for the purpose of high dispersion stability, the water-insoluble colorant having undergone the above process has a large surface functional group density even if the amount of the anionic monomer used in the above process is relatively small. And high dispersion stability can be imparted. As a result, it is possible to increase the dispersion stability of the water-insoluble colorant without impairing water resistance. The reason for this is not clear, but according to the study by the present inventors, polymerization is initiated by radicals generated in water, and oligomers are precipitated to form charged resin pseudo fine particles. The portion is preferentially oriented on the water phase side, that is, near the surface of the chargeable resin pseudo fine particles. This state is maintained even after the resin fine particles are fixed to the water-insoluble colorant, and the surface of the water-insoluble colorant of the present invention having a structurally large specific surface area further has an anionic group derived from an anionic monomer component. As a result, it is expected that the water-insoluble colorant to which the resin fine particles are fixed is stabilized with a smaller amount of anionic monomer component.

[Other ingredients in ink]
The ink according to the present invention is preferably constituted by mixing the dispersible colorant and the water-soluble resin described above in an aqueous medium, particularly a mixed medium of water and a water-soluble organic solvent.

  In the ink according to the present invention, the selection of the solvent system is important in order to adjust the storage stability of the ink, the moisture retention at the nozzle tip, and the fixing property on the recording paper. Examples of the water-soluble organic solvent that can be used in this case include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-pentanol. Alkyl alcohols having 1 to 5 carbon atoms such as amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; diethylene glycol, triethylene glycol, tetra Oxyethylene or oxypropylene copolymer such as ethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, trimethylene glycol, triethylene glycol, 1,2,6-hexanetriol; glycerin; thiodiethylene glycol; ethylene glycol monomethyl ( Or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, lower alkyl ethers such as triethylene glycol monomethyl (or ethyl) ether; triethylene glycol dimethyl (or ethyl) ether, tetraethylene glycol dimethyl (or ethyl) ether, etc. Lower dialkyl ethers of polyhydric alcohols; alkanolamines such as monoethanolamine, diethanolamine, triethanolamine; sulfora , N- methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone nitrogen-containing heterocyclic ketones such as sulfolane, sulfur-containing compounds such as dimethyl sulfoxide. Content of the said water-soluble organic solvent is 0-50 mass%, Preferably it is the range of 0-20 mass%.

  The content of water in the ink is preferably in the range of 20 to 95 mass%, particularly 60 to 95 mass% of the total mass of the ink. If the content is less than 20% by mass, there are cases where the viscosity becomes high, the ink tends to bleed on paper, and the fixing property is inferior. It can get worse. It is desirable to use deionized water rather than general water containing various ions.

  In order to improve the fixing property, an anti-fixing agent different from a conventionally used water-soluble organic solvent such as a compound having an effect of suppressing evaporation and a compound suppressing an increase in viscosity may be used. Examples of the anti-sticking agent include triethylamine salts such as urea, ethyleneurea, trimethylolpropane and triethylamine hydrochloride, triethanolamine salts such as triethanolamine hydrochloride, and toluenesulfonamide derivatives. These anti-sticking agents are preferably selected and used in the ink in the range of 0 to 30% by mass. Further, it may contain a penetrant, an antiseptic, an antifungal agent and the like for helping the permeability to the recording medium.

[Recorded image]
The ink jet recording image of the present invention is formed on a recording medium using the ink of the present invention by an ink jet recording apparatus as will be described later. As the recording medium in the present invention, any medium capable of ink jet recording can be used without limitation.

[Image recording method and recording apparatus]
The water-based ink according to the present invention is used for an ink jet discharge type head, and is effective as an ink tank in which the ink is stored or as a filling ink. 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 its 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 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 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 integrated 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. . Specific examples thereof include a capping unit for the recording head, a cleaning unit, a pressure or suction unit, an electrothermal converter, a heating element different from this, or a preheating unit using a combination thereof, This is a preliminary ejection mode in which ejection different from recording 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.

[Example 1]
A recording ink 1 according to Example 1 was prepared in the following manner. First, as a color material, a mixed liquid having a composition consisting of 10 parts of pigment blue (PB) 15: 3 (manufactured by Clariant), 6 parts of glycerin, 4 parts of a styrene-acrylic acid dispersant, and 80 parts of water The pigment dispersion 1 was obtained by dispersing for 5 hours at 1,500 rpm in a sand mill manufactured by Kogyo. In the sand mill, zirconia beads having a diameter of 0.6 mm were used as media, and the filling rate in the pot was 70% by volume. 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 1 was stably dispersed with an average dispersion particle size of 108 nm, and the polydispersity index was 0.14.

  Next, 100 parts of the above pigment dispersion 1 was used, and while being heated to 70 ° C. in a nitrogen atmosphere, a liquid having the following composition was gradually added dropwise while stirring with a motor to perform polymerization. The liquid used in this case 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, By centrifuging at 500 rpm for 2 hours, a dispersible colorant 1 as a precipitate was obtained.

  The dispersible colorant 1 is dispersed in water, centrifuged at 12,000 rpm for 60 minutes, and the precipitate re-dispersed in water is dried, and a scanning electron microscope JSM-6700 (JEOL Hi-Tech) is dried. When the dispersible colorant 1 was observed at a magnification of 50,000 times, a state where the resin fine particles were scattered and fixed on the surface of the pigment was observed. Furthermore, the B / P ratio (B / P-1) of this dispersion and the B / P ratio of this dispersion obtained by re-dispersing the sediment obtained by centrifugation at 80,000 rpm for 90 minutes. (B / P-2) was measured to obtain (B / P-2) / (B / P-1). As a result, the value of (B / P-2) / (B / P-1) was in the range of 0.5 to 1.0, and it was determined that the pigment and the resin were fixed. In the above, B / P = resin fine particle mass / pigment mass. In addition, the form of the dispersible color materials described later in this example was confirmed by the same method.

  The dispersible colorant 1 obtained above and the following components including a water-soluble resin (copolymer) were mixed so that the pigment concentration in the ink would be 0.5% (water so that the total amount would be 100 parts) Further, pressure filtration was performed with a membrane filter having a pore size of 2.5 microns (μm) to obtain a recording ink 1 of this example. The B / P ratio of the dispersible colorant in the obtained ink was 0.4, and the Ba / P ratio of the obtained ink was 2.

・ Dispersible colorant 1 Amount of pigment concentration 0.5% ・ Glycerol 7 parts ・ Diethylene glycol 5 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH (trade name: Kawaken Fine Chemical Co., Ltd.) 0.2 parts ・ Benzyl acrylate / 50% aqueous solution of methacrylic acid copolymer (molecular weight: 10,000, acid value: 200)
1.6 parts, remaining ion-exchanged water

[Example 2]
Using 100 parts of the same pigment dispersion 1 prepared in Example 1 and heating to 70 ° C. in a nitrogen atmosphere, the following liquid was gradually added dropwise with stirring by a motor, and polymerization was performed for 8 hours. went. The liquid used in this case consists of 5.7 parts of styrene, 0.3 part of acrylic acid, 0.07 part of potassium hydroxide, 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 2. The obtained dispersible colorant 2 was in a state where resin fine particles were scattered and fixed on the surface of the pigment, as in Example 1. Further, it was confirmed by the same method as in Example 1 that the pigment and the resin were fixed.

  Further, the recording of this example is performed in the same manner as in Example 1 except that the dispersible colorant 1 of the ink components is replaced with the dispersible colorant 2 so that the pigment concentration in the ink becomes 0.5%. Ink 2 was prepared. The B / P ratio of the dispersible colorant in the obtained ink was 0.4, and the Ba / P ratio of the obtained ink 2 was 2.

[Example 3]
Using 100 parts of the same pigment dispersion 1 prepared in Example 1 and heating to 70 ° C. in a nitrogen atmosphere, the following liquid was gradually added dropwise with stirring with a motor, and polymerization was performed for 5 hours. went. The liquid used at this time consists of 6 parts of butyl acrylate, 0.05 part of potassium persulfate and 20 parts of water. After polymerization for 5 hours as described above, purification was performed by centrifugation in the same manner as in Example 1 to obtain dispersible colorant 3. When the dispersible colorant 3 obtained by the same method as in Example 1 was observed, it was observed that the resin fine particles were fixed to the surface of the pigment even in the dispersible colorant 3. However, compared with the case of Example 1, it has confirmed that there were many parts fused. Further, it was confirmed by the same method as in Example 1 that the pigment and the resin were fixed.

  Further, in the same manner as in Example 1 except that the dispersible colorant 1 is replaced with the dispersible colorant 3 among the ink components so that the pigment concentration in the ink becomes 0.5%, the recording Ink 3 was prepared. The B / P ratio of the dispersible colorant in the obtained ink was 0.4, and the Ba / P ratio of the obtained ink 3 was 2.

[Example 4]
Using 100 parts of the same pigment dispersion 1 prepared in Example 1 and heating to 70 ° C. in a nitrogen atmosphere, the following liquid was gradually added dropwise with stirring with a motor, and polymerization was performed for 5 hours. went. The liquid used at this time 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 polymerization for 7 hours as described above, purification was performed by centrifugation in the same manner as in Example 1 to obtain dispersible colorant 4. The obtained dispersible colorant 4 was in a state where resin fine particles were scattered and fixed on the surface of the pigment, as in Example 1. Further, it was confirmed by the same method as in Example 1 that the pigment and the resin were fixed.

  Further, in the same manner as in Example 1 except that the dispersible colorant 1 is replaced with the dispersible colorant 4 among the ink components so that the pigment concentration in the ink becomes 0.5%, the recording Ink 4 was prepared. The B / P ratio of the dispersible colorant in the obtained ink was 0.4, and the Ba / P ratio of the obtained ink was 2.

[Examples 5 to 8]
Using each of the dispersible color materials 1 to 4 obtained in Examples 1 to 4, each dispersible color material and water-soluble resin (copolymer) were adjusted so that the pigment concentration in the ink was 0.8%. ), And the following components are mixed (adjusted with water so that the total amount becomes 100 parts), and further filtered under pressure with a membrane filter having a pore size of 2.5 microns (μm), and recording of Examples 5 to 8 Inks 5 to 8 were obtained. The B / P ratios of the dispersible colorants in the obtained inks 5 to 8 were all 0.4, and the Ba / P ratios of the inks 5 to 8 were all 1.5.

・ Dispersible colorant 1 to 4 Pigment concentration is 0.8% ・ Glycerol 7 parts ・ Diethylene glycol 5 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH (trade name: Kawaken Fine Chemical Co., Ltd.) 0.2 part ・Benzyl acrylate / methacrylic acid / ethoxyethylene glycol methacrylate copolymer (molecular weight:
12,000, acid value: 250) 50% aqueous solution
1.76 parts, balance of ion-exchanged water

[Example 9]
A recording ink 9 according to Example 9 was produced in the following manner. First, a mixed liquid composed of 10 parts of Pigment Red 122, 6 parts of glycerin, 10 parts of styrene-acrylic acid resin dispersant, and 74 parts of water was mixed at 1,500 rpm for 5 hours in a sand mill manufactured by Kanada Rika Kogyo Co., Ltd. Dispersion was performed to obtain Pigment Dispersion Liquid 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% by volume. 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 pigment dispersion 2 thus obtained was stably dispersed with an average dispersion particle size of 98 nm, and the polydispersity index was 0.15.

  Next, 100 parts of the pigment dispersion 2 obtained above was heated to 70 ° C. in a nitrogen atmosphere, and the following liquid was gradually added dropwise with stirring with a motor, and polymerization was performed for 5 hours. It was. The liquid used in this case consists 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. The obtained dispersion was diluted 10 times with water and centrifuged at 5,000 rpm for 10 minutes to remove aggregated components. Then, the dispersible color material 5 which is a sediment was obtained by further centrifuging at 12,500 rpm for 2 hours.

  The dispersible colorant 5 obtained above was dispersed in water, centrifuged at 12,000 rpm for 60 minutes, and the sediment redispersed in water, dried, and scanned by electron microscope JSM-6700. When observed at a magnification of 50,000 times (manufactured by JEOL Hitec Co., Ltd.), it was observed that the dispersible colorant 5 was scattered and fixed on the surface of the pigment with resin fine particles. Furthermore, the B / P ratio (B / P-1) of this dispersion and the B / P ratio of the dispersion obtained by re-dispersing the sediment obtained by centrifugation at 8,0000 rpm for 90 minutes. (B / P-2) was measured to obtain (B / P-2) / (B / P-1). As a result, the value of (B / P-2) / (B / P-1) was in the range of 0.5 to 1.0, and it was determined that the pigment and the resin were fixed. In the above, B / P = resin fine particle mass / pigment mass.

  Next, the following components including the dispersible colorant 5 and the water-soluble resin (copolymer) obtained above were mixed so that the pigment concentration in the ink was 0.5% by mass (total amount: 100 parts). Then, it was filtered under pressure through a membrane filter having a pore size of 2.5 microns (μm) to obtain a recording ink 9 of this example. The B / P ratio of the dispersible colorant in the obtained ink was 0.4, and the Ba / P ratio of the obtained ink was 2.

・ Dispersible colorant 5 Amount of pigment concentration 0.5% ・ Glycerol 7 parts ・ Diethylene glycol 5 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH (trade name: Kawaken Fine Chemical Co., Ltd.) 0.2 parts ・ Benzyl acrylate / 50% aqueous solution of methacrylic acid copolymer (molecular weight: 10,000, acid value: 200)
1.6 parts, remaining ion-exchanged water

[Example 10]
Using the dispersible color material 1 obtained in Example 1, the following components including the dispersible color material and the water-soluble resin (copolymer) were added so that the pigment concentration in the ink was 0.5%. The mixture was mixed (adjusted with water so that the total amount would be 100 parts), and further filtered under pressure through a membrane filter having a pore size of 2.5 microns (μm) to obtain a recording ink 10 of Example 10. The B / P ratio of the dispersible colorant in the obtained ink 10 was 0.4, and the Ba / P ratio of the ink 10 was 1.1.

・ Dispersible colorant 1 Amount of pigment concentration 0.5% ・ Glycerol 7 parts ・ Diethylene glycol 5 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH (trade name: Kawaken Fine Chemical Co., Ltd.) 0.2 parts ・ Benzyl acrylate / Methacrylic acid / Ethoxyethylene glycol methacrylate copolymer (Molecular weight:
12,000, acid value: 250) 50% aqueous solution
0.7 parts, balance of ion-exchanged water

[Comparative Example 1]
The same formulation as in Example 1 containing components such as a water-soluble resin (copolymer) so that the pigment dispersion 1 prepared in Example 1 before the polymerization step is used and the pigment has a concentration of 0.5% Comparative ink 1 was prepared. The Ba / P ratio of Comparative Ink 1 was 2. However, when the color material in the comparative ink 1 was observed in the same manner as in Example 1, no resin fine particles adhering to the surface of the color material were observed.

[Comparative Example 2]
Similar to Example 1 except that the pigment dispersion 1 prepared in Example 1 before the polymerization step was replaced with ion-exchanged water so that the water-soluble resin (copolymer) was replaced with ion-exchanged water so that the pigment had a concentration of 0.5%. Comparative ink 2 was prepared. The comparative ink 2 obtained had a Ba / P ratio of 0.4. Further, when the color material in the comparative ink 2 was observed in the same manner as in Example 1, no resin fine particles adhering to the surface of the color material were observed.

[Comparative Example 3]
The dispersible colorant 1 after the polymerization process prepared in Example 1 is different from Example 1 except that the water-soluble resin (copolymer) is replaced with ion-exchanged water so that the pigment has a concentration of 0.5%. A comparative ink 3 was prepared by the same formulation. The comparative ink 3 obtained had a Ba / P ratio of 0.4. Further, when the color material in the comparative ink 3 was observed in the same manner as in Example 1, resin fine particles adhering to the surface of the color material were observed.

[Comparative Example 4]
Using the dispersible color material 1 obtained in Example 1, the following components including the dispersible color material and the water-soluble resin (copolymer) were added so that the pigment concentration in the ink was 0.5%. The mixture was mixed (adjusted with water so that the total amount became 100 parts), and further filtered under pressure with a membrane filter having a pore size of 2.5 microns (μm) to obtain Comparative Ink 4 of Comparative Example 4. The B / P ratio of the dispersible colorant in the obtained comparative ink 4 was 0.4, and the Ba / P ratio of the comparative ink 4 was 1.0.

・ Dispersible colorant 1 Amount of pigment concentration 0.5% ・ Glycerol 7 parts ・ Diethylene glycol 5 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH (trade name: Kawaken Fine Chemical Co., Ltd.) 0.2 parts ・ Benzyl acrylate / Methacrylic acid / Ethoxyethylene glycol methacrylate copolymer (Molecular weight:
12,000, acid value: 250) 50% aqueous solution
0.5 parts, balance of ion-exchanged water

[Dispersible color ink characteristics]
With respect to the ink dispersible color materials of Examples 1 to 10 and Comparative Examples 1 to 4, the observation and various physical properties were measured by the methods described below, and the obtained results are shown in Tables 1 and 2. Indicated. Only a part of the ink of the comparative example was performed.

<Average particle size>
The dispersible colorant used in each ink 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 diameter.

<Glass transition temperature: Tg (° C.)>
The glass transition temperature of the resin fine particles fixed to the color material in each ink was measured with a DSC 822e manufactured by METTLER TOLEDO using a sample obtained by drying each dispersible color material.

<Resin fine particle mass / pigment mass (B / P ratio)>
The value of the B / P ratio of the dispersible colorant in each ink was determined by differential thermogravimetry. A dispersible colorant was separated from the ink by centrifugation at 5,000 rpm for 10 minutes and further at 12,500 rpm for 2 hours, and the sediment was dried, and a sample was used as a TGA / SDTA851 manufactured by METTLER TOLEDO. Measured and calculated.

<Total resin mass / pigment mass (Ba / P ratio)>
The value of Ba / P ratio of each ink was determined by differential thermogravimetry. A sample obtained by drying the ink for 24 hours with a 60 ° C. dryer was measured and calculated with a TGA / SDTA851 manufactured by METTLER TOLEDO.

<Surface functional group density>
The surface functional group density of each dispersible colorant in each ink 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 bicarbonate and pure water from the neutralization amount obtained by neutralization titration with 0.1 N HCl. When it was clear that a cationic group was included as the polar group, the same procedure was used to determine sodium hydroxide instead of hydrochloric acid and ammonium chloride instead of sodium bicarbonate.

<Surface energy>
The dispersible colorant in each ink is separated by centrifugation, dried, crushed and used as a measurement sample, packed in a column, and probe gas is removed using an inverse gas chromatograph manufactured by Surface Measurement System. It measured as hexane, heptane, pentane, chloroform, ethanol, and acetone, respectively, and calculated | required by extrapolating the plot of each support time.

[Ink evaluation method and evaluation results]
Using the recording inks of Examples 1 to 9 and Comparative Examples 1 to 3 obtained by the method described above, printing on a recording medium was performed with an ink jet recording apparatus, and the obtained images were evaluated. The ink jet recording apparatus used was BJ S600 (manufactured by Canon Inc.), and an image was formed on the glossy recording medium HG-201 (manufactured by Canon Inc.) using the apparatus. The recording head used here has a recording density of 360 dpi and a driving frequency of 5 kHz. A head with a discharge volume per dot of 60 pl / dot was used. And the abrasion resistance and light resistance of the printed matter obtained by printing on the said conditions were evaluated by the following method, and the result was shown in Table 1 and Table 2.

<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 (400 kg / m ² ) 5 times, visually observing the disorder of the printed portion. .
A: Prints are not disturbed due to rubbing and white portions are not smeared B: Prints are not disturbed due to rubbing and white portions are hardly smeared and are not noticeable C: Prints are greatly disturbed by rubbing and white portions are smeared

<Light resistance>
Using the super xenon SX-75 (manufactured by Suga Test Instruments), an accelerated light resistance test was performed on the printed matter obtained with the above apparatus with a xenon lamp for up to 300 hours. The deterioration of the image portion was visually observed and evaluated according to the following criteria.
A: Image degradation is not known B: Image is slightly faint but not noticeable C: Clearly clear image

  In any Examples, as a result of observing the color material, it was confirmed that a dispersible color material having single dispersibility was obtained. In addition, in any of the inks using these dispersible color materials, printed matter having excellent print quality and excellent scratch resistance was obtained. In particular, in Examples 1, 2, 4, 5, 6, 8, and 9 in which the Ba / P ratio was high and the surface functional group density of the dispersible colorant was high, printed matter having excellent scratch resistance was obtained. . On the other hand, in Comparative Example 1, since the chargeable resin pseudo fine particles were not attached to the pigment as compared with the Example, the obtained printed matter was inferior in image scratch resistance. In Comparative Example 2, since the charged resin pseudo fine particles are not adhered to the pigment, and the Ba / P ratio is small and the amount of the resin is insufficient, the obtained printed matter has an image scratch resistance and light resistance. Both were inferior. In Comparative Example 3, the chargeable resin pseudo fine particles are adhered to the pigment, but the Ba / P ratio is small and the amount of resin is insufficient. Therefore, the obtained printed matter has an image scratch resistance and light resistance. It was inferior.

It is a schematic diagram which shows the basic structure of the dispersible color material which has fixed the chargeable resin pseudo fine particles by this invention. It is a schematic diagram of the typical process in the manufacturing method of this invention. It is a schematic diagram which shows the refinement | purification of the chargeable resin pseudo fine particles and the adhering process to a color material in the manufacturing method of this invention. It is the schematic diagram which expanded the chargeable resin pseudo fine particle of this invention from the interface side fixed to a coloring material.

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 particles 9-2: Hydrophobic monomer unit portion 10 in the charged resin pseudo fine particles 10: Bonding site with the coloring material

Claims (18)

  A water-based inkjet recording ink comprising a water-insoluble colorant and a dispersible colorant composed of one or more kinds of chargeable resin pseudo fine particles and a water-soluble resin, wherein the dispersible colorant is the water-insoluble colorant. Are dispersed alone by fixing the chargeable resin pseudo fine particles, and the concentration of the water-insoluble colorant in the ink is 1% by mass or less of the total mass of the ink, and the resin content in the ink is A water-based inkjet recording ink, wherein the ratio (Ba / P ratio) of the total mass (Ba) to the mass (P) of the water-insoluble colorant in the ink is greater than 1.   A water-based inkjet recording ink comprising a water-insoluble colorant and a dispersible colorant composed of one or more kinds of chargeable resin pseudo fine particles and a water-soluble resin, wherein the dispersible colorant is the water-insoluble colorant. Are dispersed alone by being scattered and fixed with the above-mentioned chargeable resin pseudo fine particles, and the concentration of the water-insoluble colorant in the ink is 1% by mass or less of the total mass of the ink, and the ink A water-based inkjet recording ink, wherein the ratio (Ba / P ratio) of the total mass (Ba) of the resin content in the ink to the mass (P) of the water-insoluble colorant in the ink is greater than 1.   The water-based inkjet recording ink according to claim 1, wherein the chargeable resin pseudo fine particles have a polar group.   The aqueous inkjet recording ink according to claim 3, wherein the polar group is an anionic group or a cationic group.   The water-based inkjet recording ink according to any one of claims 1 to 4, wherein a surface functional group density of the dispersible colorant is 250 µmol / g or more and less than 1,000 µmol / g. The water-based inkjet recording ink according to claim 1, wherein the dispersible colorant has a surface energy of 70 mJ / m ² or less.   The chargeable resin pseudo fine particle comprises a copolymer component synthesized from a monomer component containing at least one kind of hydrophobic monomer and at least one kind of hydrophilic monomer. The water-based inkjet recording ink according to Item.   The aqueous inkjet recording ink according to claim 7, wherein the copolymer component has a glass transition temperature of −60 ° C. or higher and 120 ° C. or lower.   The aqueous inkjet recording ink according to claim 7 or 8, wherein the hydrophobic monomer contains at least a monomer having a methyl group at the α-position and having a radical polymerizable unsaturated double bond.   The aqueous inkjet recording ink according to any one of claims 7 to 9, wherein the hydrophobic monomer contains at least a (meth) acrylic acid ester compound.   The water-based inkjet recording ink according to claim 10, wherein the hydrophobic monomer contains at least one selected from benzyl methacrylate or methyl methacrylate.   The aqueous inkjet recording ink according to any one of claims 7 to 11, wherein the hydrophilic monomer contains at least an anionic monomer.   The water-based inkjet recording ink according to claim 12, wherein the anionic monomer contains at least one selected from acrylic acid, methacrylic acid, p-styrenesulfonic acid, and salts thereof.   The water-soluble resin comprises a copolymer component synthesized from a monomer component containing at least one hydrophobic monomer and at least one hydrophilic monomer, and the hydrophilic monomer is an anionic monomer. The ink for water-based inkjet recording of any one of Claims 1-13 containing at least.   The aqueous inkjet recording ink according to claim 14, wherein the anionic monomer contains at least one selected from acrylic acid and methacrylic acid.   In an ink jet recording apparatus in which image formation is performed by applying ink onto a recording medium by an ink jet recording method, the ink is the ink for ink jet recording according to any one of claims 1 to 15. Inkjet recording device.   An ink jet recording method for forming an image by applying ink on a recording medium by an ink jet recording method, wherein the ink for ink jet recording according to any one of claims 1 to 15 is used as the ink. Recording method. An inkjet recording image formed by applying ink onto a recording medium by an inkjet recording method, wherein the ink is the inkjet recording ink according to any one of claims 1 to 15. image.

Images