JP2005263953A - Aqueous colorant dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet excellent in storage stability and color reproducibility in forming images, and to provide an aqueous colorant dispersion used as a raw material for it. <P>SOLUTION: The aqueous colorant dispersion is the one in which the capsule particles, obtained by having the surface of colorant particles coated with a resin, is dispersed in an aqueous medium. Herein, the above resin is a block copolymer consisting of at least one hydrophilic block and at least one hydrophobic block and an organic solvent is present in the above capsules. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aqueous color material dispersion and an inkjet ink.

  As ink-jet inks, water-based inks are mainly used in terms of safety and the like, and water-based inks using water-soluble dyes are most popular because of their excellent color developability. However, the water-based ink using the water-soluble dye has poor water resistance because the dye is water-soluble, and because the dye is molecular, light, ozone, etc. There is a problem that the image is rapidly deteriorated by the gas.

  In order to solve these problems, a dispersion-type ink using a color material such as a pigment or a sparingly soluble dye in which a color material is not in the form of a molecule but has a form in which a plurality of molecules are assembled has been studied. An image formed from these inks is superior to an image formed from a water-soluble dye ink in so-called image fastness such as water resistance, light resistance, and gas resistance. There are problems such as particle size non-uniformity and storage stability, color material particle sedimentation, clogging at the ink ejection port, and irregular reflection due to aggregation of color material particles. Easy to wake up.

  Therefore, in order to stably disperse the water-insoluble or hardly soluble coloring material in the aqueous medium, the block co-polymer containing a portion that is easily adsorbed on the surface of the coloring material particles and a portion that has a high affinity for the aqueous medium. An aqueous dispersion using a polymer or graft copolymer as a dispersant has been proposed. For example, Patent Document 1 discloses a pigment dispersion obtained by combining a pigment and a block copolymer, and Patent Document 2 discloses a pigment dispersion obtained by combining a pigment and a graft copolymer. Furthermore, there is a technique in which a water-insoluble oil-soluble dye is dissolved in an organic solvent and then mixed with a block copolymer, and water is added thereto to make the medium aqueous and thereby deposit the oil-soluble dye as fine particles. 3 is disclosed.

  In these techniques, the dispersion stability of the colorant particles is improved by the action of a block copolymer or a graft copolymer having a block having an affinity for each of the water-insoluble colorant and the aqueous medium. However, since the original dispersibility of the colorant greatly contributes to the formation of these dispersions, pigments that require fine pulverization and oil-soluble dyes that re-form fine particles have a uniform particle size dispersion. It is not easy to obtain a body, and in the long term, the dispersion may have a non-uniform particle size distribution that leads to aggregation and sedimentation. In addition, due to the non-uniformity of the coloring material, particularly oil-soluble dyes, the dispersed particles are re-aggregated from the dissolved molecular state, and therefore accompanied by changes in hue and color developability depending on the form after aggregation, When an image is formed, a problem is likely to occur in color reproducibility.

JP-A-5-179183 JP-A-9-188732 JP 2002-97395 A

  In view of the above situation, an object of the present invention is to provide an inkjet ink having excellent storage stability and excellent color reproducibility when an image is formed, and an aqueous color material dispersion as a raw material thereof. To do.

  The above object can be achieved by the present invention described below. That is, the present invention provides a color material dispersion in which capsule particles whose surfaces of color material particles are coated with a resin are dispersed in an aqueous medium, wherein the resin includes at least one hydrophilic block and at least one hydrophilic block. A water-based colorant dispersion comprising: a block copolymer comprising a hydrophobic block, wherein an organic solvent is present in the capsule.

  In the aqueous color material dispersion of the present invention, the organic solvent is an aprotic polar solvent; the block copolymer is a block copolymer having a polyvinyl ether structure; and the color material is A water-insoluble colorant is preferable. The present invention also provides an ink-jet ink comprising the aqueous color material dispersion of the present invention as a colorant.

  In the present invention, the colorant is a water-insoluble or hardly soluble pigment or dye, and takes a fine particle form in an aqueous medium. Therefore, the image formed by the ink comprising the color material dispersion of the present invention is higher in water resistance, light resistance and gas resistance than the image obtained by using the water-soluble dye dissolved in the molecular dispersion state as the color material. Moreover, there is little deterioration of the hue after image formation by forming into particles.

  Further, in a preferred embodiment of the present invention, when an aprotic polar solvent is used when the aqueous color material dispersion of the present invention is produced, a dispersion in which color material fine particles are encapsulated with a block copolymer is formed. In the process, the solvent is included in the capsule in the same manner as the colorant fine particles. By using an aprotic polar solvent, the polarization of the surface of the colorant fine particles is strengthened in the capsule formation stage, and the cohesiveness of the colorant fine particles is reduced, which leads to miniaturization and uniform particle size of the capsule particles. . Furthermore, by including the above-mentioned solvent together with the coloring material in the capsule, the solvation of the chromophore of the coloring material is limited, the polarization transition state is stabilized, and as a result, the high coloring property comparable to the ink using the water-soluble dye is achieved. Will get.

  Further, the present invention uses a block copolymer comprising at least one hydrophilic block and at least one hydrophobic block as the resin in the colorant dispersion, whereby the hydrophobic property of the block copolymer is determined. The functional block acts to adsorb or enclose the color material fine particles on the surface of the color material fine particles, while the hydrophilic block has a high affinity with an aqueous medium, so that it is stably in the liquid in the capsule state holding the color material fine particles. Allows to be distributed.

  Further, the block copolymer is preferably a vinyl copolymer, the vinyl copolymer has a chemically strong main chain structure, and by appropriately selecting a side chain bonded to the main chain, Various properties such as the balance between hydrophilicity and hydrophobicity, the viscosity of the ink, and the fixability of the ink to the recording medium during printing can be designed.

  According to the present invention, it is possible to provide an aqueous color material dispersion and an ink jet ink which are excellent in storage stability and serve as a raw material for an aqueous ink having excellent color reproducibility when an image is formed.

Next, the present invention will be described in more detail with reference to preferred embodiments.
As the water-insoluble color material used in the present invention, any color material that hardly dissolves in water can be used. Specifically, the colorant has a solubility in water of preferably 0.5% by mass or less, more preferably 0.1% by mass or less. Examples of such a color material include oil-soluble dyes, vat dyes, disperse dyes, and pigments, but color materials newly synthesized for the present invention may be used.

Examples of water-insoluble colorants are shown below, but the present invention is not limited to these.
(Oil-soluble dye)
C. I. Solvent Yellow 1, 2, 3, 13, 14, 19, 21, 22, 29, 36, 37, 38, 39, 40, 42, 43, 44, 45, 47, 62, 63, 71, 76, 79, 81, 82, 83: 1, 85, 88, 86, 151; I. Solvent Red 8, 27, 35, 36, 37, 38, 39, 40, 49, 58, 60, 65, 69, 81, 83: 1, 86, 89, 91, 92, 97, 99, 100, 109, 118, 119, 122, 127, 218; I. Solvent Blue 14, 24, 25, 26, 34, 37, 38, 39, 42, 43, 44, 45, 48, 52, 53, 55, 59, 67, 70; C.I. I. Solvent black 3, 5, 7, 8, 14, 17, 19, 20, 22, 24, 26, 27, 28, 29, 45, 43, and the like.

(Vat dyes)
C. I. Vat Yellow 2, 4, 10, 20, 33; I. Vat Orange 1, 2, 3, 5, 7, 9, 13, 15; I. Vat Red 1, 2, 10, 13, 15, 16, 61; I. Bat Blue 1, 3, 4, 5, 6, 8, 12, 14, 18, 19, 20, 29, 35, 41; C.I. I. Bat Black 1, 8, 9, 13, 14, 20, 25, 27, 29, 36, 56, 57, 59, 60, etc.

(Disperse dye)
C. I. Disperse Yellow 5, 42, 83, 93, 99, 198, 224; I. Disperse Orange 29, 49, 73; C.I. I. Disperse Red 92, 126, 145, 152, 159, 177, 181, 206, 283; I. Disperse Blue 60, 87, 128, 154, 201, 214, 224, 257, 287, 368, etc.

(Pigment)
C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153, 154, 166, 168, 180, 185; I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71; C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272; I. Pigment violet 19, 23, 29, 30, 37, 40, 50; C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64; C.I. I. Pigment green 7, 36; I. Pigment brown 23, 25, 26, and the like.

  The solvent used in the present invention is preferably an aprotic polar solvent. Examples of the aprotic polar solvent include N, N-dimethylformamide, acetone and acetonitrile, as well as N, N-dimethylsulfoxide, N, N-dimethylacetamide, methylformamide, sulfolane, hexamethylphosphoric triamide, and nitrobenzene. However, the present invention is not limited to these solvents. Further, since these solvents are required to remain in the ink even under conditions where water evaporates, it is desirable that the boiling point is higher than that of water. However, these solvents are not necessarily limited to high-boiling substances because they have an interaction with the block copolymer and thus are less likely to evaporate than when used alone.

  The present invention relates to an aqueous color material dispersion containing a color material, a resin, an organic solvent, and water, and an ink for an ink jet printer using the aqueous color material dispersion as a raw material. It is a block copolymer of a polyvinyl ether structure containing a functional block and a hydrophobic block.

The block copolymer used in the present invention has at least one hydrophilic block (A) and hydrophobic block (B), respectively.
The arrangement of each block in the block copolymer is not particularly limited, but those having a hydrophilic block at the end of the polymer chain are preferred from the viewpoint of enhancing the dispersibility of the coloring material. Examples include AB type, ABA ′ type (A and A ′ may be the same or different), AA′B type, BB′A type (B and B ′ may be the same or different), and the like. . A, A ′, B, and B ′ are homopolymer or copolymer blocks.

The block copolymer used in the present invention is a block copolymer comprising a hydrophilic block composed of a homopolymer or copolymer of a vinyl ether monomer and a hydrophobic block composed of a homopolymer or copolymer of a vinyl ether monomer.
These polymers preferably have, for example, a repeating unit structure represented by the following general formula (1).
^{_{- (CH 2 -CH (OR 1}} )) - (1)
In the general formula (1), R ¹ represents an aliphatic hydrocarbon such as an alkyl group, an alkenyl group, a cycloalkyl group, or a cycloalkenyl group, a phenyl group, a pyridyl group, a benzyl group, a toluyl group, a xylyl group, An aromatic hydrocarbon group in which a carbon atom may be substituted with a nitrogen atom, such as an alkylphenyl group, a phenylalkylene group, a biphenyl group, and a phenylpyridyl group. Moreover, the hydrogen atom on the aromatic ring may be substituted with a hydrocarbon group. R ¹ preferably has 1 to 18 carbon atoms.

R ¹ may be a group represented by — (CH (R ² ) —CH (R ³ ) —O) _p —R ⁴ or — (CH ₂ ) _q — (O) _r —R ⁴ . In this case, R ² and R ³ each independently represent a hydrogen atom or a methyl group, and R ⁴ represents an aliphatic hydrocarbon such as an alkyl group, an alkenyl group, a cycloalkyl group, or a cycloalkenyl group, a phenyl group, Aromatic hydrocarbon groups in which carbon atoms may be substituted with nitrogen atoms, such as pyridyl group, benzyl group, toluyl group, xylyl group, alkylphenyl group, phenylalkylene group, biphenyl group, phenylpyridyl group (aromatic The hydrogen atom on the ring may be substituted with a hydrocarbon group), —CHO, —CH ₂ CHO, —CO—CH═CH ₂ , —CO—C (CH ₃ ) ═CH ₂ , —CH ₂ —CH═CH ₂ , —CH ₂ —C (CH ₃ ) ═CH ₂ , —CH ₂ —COOR ^5, etc., and the hydrogen atom in these groups is fluorine, as long as it is chemically possible. Chlorine, odor Halogen atoms and may be substituted, such as. R ⁴ preferably has 3 to 18 carbon atoms. R ⁵ is hydrogen or an alkyl group. p is preferably 1 to 18, q is preferably 1 to 36, and r is preferably 0 or 1.

In R ¹ and R ⁵ , examples of the alkyl group or alkenyl group include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl. , Tetradecyl, hexadecyl, octadecyl, oleyl and the like, and examples of the cycloalkyl group or cycloalkenyl group include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl and the like.

  Examples of the structures of the monomer (Ia to Io) and the polymer (II-a to II-e) containing the repeating unit described above are illustrated below. The polyvinyl ether structure used in the present invention includes these It is not limited to.

  Furthermore, it is preferable that the number of repeating units of polyvinyl ether (in the following (II-a) to (II-e), m, n, and l) is independently 1 or more and 10,000 or less, The total (in the following (II-a) to (II-e), m + n or m + n + 1) is more preferably 10 or more and 20,000 or less, and the number average molecular weight is 500 or more and 20,000,000. The following is preferred. More preferably, the number average molecular weight is 1,000 or more and 5,000,000 or less. More preferably, the number average molecular weight is 2,000 or more and 2,000,000 or less. In addition, these polyvinyl ether block copolymers may be those obtained by grafting them to other polymers, or may be those copolymerized with other repeating units (monomers). Good.

Many methods for synthesizing a polymer containing a polyvinyl ether structure have been reported (for example, JP-A-11-080221), but a method by cationic living polymerization by Aoshima et al. (Polymer Bulletin, Vol. 15, 1986, page 417, Representative are Japanese Patent Application Laid-Open No. 11-322942 and Japanese Patent Application Laid-Open No. 11-322866. By conducting polymer synthesis by cation living polymerization, various polymers such as homopolymers, copolymers composed of two or more monomers, and block polymers, graft polymers, and gradient polymers can be used with different lengths (molecular weights). It can be accurately aligned and synthesized. In addition, various functional groups can be introduced into the side chain of polyvinyl ether. The cationic polymerization method can also be carried out in the HI / I ₂ system, HCl / SnCl ₄ system, or the like.

  In these polyvinyl ether block copolymers, the hydrophobic block has affinity for the colorant and interacts strongly with the colorant surface, while the hydrophilic block stabilizes dispersion in aqueous ink. At the same time, when it is applied to a recording medium, it has a property of being strongly fixed to the recording medium. Here, the smaller the molecular weight of the hydrophilic block portion is, the more advantageous is to avoid the phenomenon such as gelation while keeping the viscosity of the ink low, and conversely, the larger the molecular weight of the hydrophilic block portion is to the recording medium. Fixing power increases. The ratio of the molecular weight of the hydrophilic block to the total molecular weight of the polyvinyl ether block copolymer of the present invention is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass. In this range, sufficient effects can be obtained for both dispersion stability and fixing power. Moreover, such a characteristic has a favorable range that varies depending on the structure of the main chain of the polymer and the glass transition temperature.

  The water-based color material dispersion of the present invention can be obtained by using the water-insoluble color material, the aprotic polar solvent, and the block copolymer in appropriate proportions. The proportion of these components used is preferably 1.0 to 50 parts by mass of the aprotic polar solvent when the water-insoluble colorant is 100 parts by mass. When the amount of the aprotic polar solvent used is less than 1.0 part by mass, the above-described effects of the present invention may not be sufficiently obtained. On the other hand, when the amount of the aprotic polar solvent used exceeds 50 parts by mass. , The presence of the coloring material particles or on the surface of the molecule reduces the hydrophobicity of the coloring material itself, weakens the attraction with the hydrophobic portion of the block copolymer, hinders the formation of the capsule dispersion, It is not preferable in terms of destabilization.

  Moreover, it is preferable to use the said block copolymer in the ratio of 20-200 mass parts, when a water-insoluble coloring material is 100 mass parts. When the amount of the block copolymer used is less than 20 parts by mass, the dispersibility and dispersion stability of the colorant fine particles in the resulting dispersion are insufficient, and the colorant particles may settle or aggregate during long-term storage. There is. On the other hand, when the amount of the block copolymer used exceeds 200 parts by mass, the dispersibility and dispersion stability of the colorant particles are not improved according to the amount, which is not economical.

  The aqueous color material dispersion of the present invention may be produced by any method. For example, first, an aprotic polar solvent in the above range is added to the water-insoluble coloring material, and both are mixed uniformly. Normally, this mixture is not liquid, but in a wet powder state wet with a solvent. For example, the color material is made fine by grinding with a roll mill, ball mill, vibration mill, etc. and the solvent is adsorbed to the color material particles. Let On the other hand, a predetermined amount of the block copolymer is dissolved or dispersed in an aqueous medium (water or a mixture of water and a water-soluble organic solvent). In this case, the concentration of the block copolymer is preferably about 0.2 to 20% by mass.

  The wet powder color material adsorbed with the aprotic polar solvent is added to the aqueous medium solution or dispersion of the block copolymer, or vice versa, and both are mixed uniformly. As a means for mixing, a known disperser for dispersing a pigment or the like, for example, an ultrasonic disperser, a bead mill, a ball mill, or the like can be used. After the dispersion treatment, the aqueous color material dispersion of the present invention is obtained by removing coarse particles by a centrifuge or a filter as necessary. The concentration of the color material in the dispersion is not particularly limited, but a concentration of about 0.2 to 20% by mass is usually convenient for use. In the dispersion thus obtained, the hydrophobic block of the block copolymer is adsorbed on the surface of the color material particles on which the solvent is adsorbed, and the color material particles are coated to form capsules. ing. The surface of the capsule has a hydrophilic block of a block copolymer and is compatible with an aqueous medium. Accordingly, the color material particles of the color material dispersion of the present invention are stably dispersed in an aqueous medium for a long period of time due to the capsule structure, and settling and aggregation of the color material particles are prevented. Furthermore, since the color material particles are dispersed in a state of being coated with the block copolymer, when coating or printing is performed using this dispersion, the resulting coated or printed material has a weather resistance inherent to the color material. In addition to the properties, the effect of the coating of the block copolymer is added, and higher weather resistance is imparted.

The water-based color material dispersion of the present invention has a polydispersity index usually obtained by analyzing the particle size distribution of the particles by a cumulant method, which is generally 0.3 or less. Is preferably 0.2 or less, more preferably 0.15 or less. Here, the “polydispersity index” is a value obtained by a dynamic light scattering method, and is a value obtained from a calculation formula of μ / G ² . μ is a value of the second-order coefficient of the cumulant method, and G represents an attenuation constant of the cumulant method. When the polydispersity index exceeds 0.3, the particle size distribution of the dispersion is wide, and those having a large particle size are also present in the dispersion. When the dispersion is used as an ink, the ejection stability of the ink Is not preferable because it tends to deteriorate. The same applies to the particle diameter. For glossiness and clear image formation, the particle diameter is preferably 10 to 200 nm, and particularly preferably in the range of 50 to 150 nm.

  The above-described aqueous color material dispersion of the present invention is useful for various applications such as printing inks and paints, but is particularly useful as a colorant for inkjet inks. That is, the water-based color material dispersion can be made into an ink jet ink by further adding an appropriate water-soluble organic substance as required. The amount of the color material in the ink is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass. If the amount of the color material is less than 0.1% by mass, a sufficient density cannot be obtained in the printed image. If the amount of the color material exceeds 20% by mass, the image density does not increase greatly, but the nozzle is clogged. Ink discharge stability is lowered.

  The organic substance added to the ink mainly serves to prevent the ink from solidifying due to drying at the nozzle portion of the ink jet printer and stabilize the ejection. Specifically, alcohols such as isopropanol and butanol; ethylene glycol , Diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, thiodiglycol, neopentyl glycol Diols such as 1,4-cyclohexanediol and polyethylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether , Alkylene glycol monoalkyl ethers such as ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether Polyols such as glycerin, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, pentaerythritol; tetrahydrofuran, dioxane, etc. Cyclic ethers of dimethyl sulfoxide, diacetone alcohol, Serine monoallyl ether, N-methyl-2-pyrrolidone, 2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, sulfolane, urea, β-dihydroxyethylurea, acetonylacetone, dimethylformamide, Examples thereof include dimethylacetamide and phenoxyethanol.

  Such an organic substance may be solid or liquid as long as it is water-soluble. Further, since it is required to remain in the ink even under conditions where water evaporates, the boiling point is preferably higher than that of water, and preferably 120 ° C. or higher. Since it has an effect, it is harder to evaporate than a single substance, so that it is not necessarily limited to a high boiling point substance. These organic substances may be used alone or in combination of two or more. The proportion of these organic substances in the ink is 5 to 50% by mass, preferably 10 to 30% by mass, based on the total mass of the ink. In addition to the above-described components, various additives such as a surfactant, a pH adjuster, an antioxidant, and an antifungal agent may be added to the aqueous color material dispersion and ink of the present invention.

  The ink of the present invention can be suitably used in an ink jet recording method in which energy is applied to the ink to cause it to fly. As energy, thermal energy or mechanical energy can be used, but a method using thermal energy is particularly preferable. As a printer for inkjet recording, it can be applied to a printer for general households mainly using A4 size paper, a printer for printing business cards and cards, or a large printer for business use. It is suitably used for large machines that require a large amount of ink. As a recording medium for recording with the ink of the present invention, plain paper without special coating, so-called ink jet exclusive paper coated with a layer for receiving ink on at least one side, postcard, business card paper, label paper, cardboard paper And an inkjet film.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the following description, “parts” or “%” are based on mass unless otherwise specified. In the following examples, the average particle size was measured using a dynamic light scattering method (trade name: Laser particle size analysis system PAR-III; manufactured by Otsuka Electronics Co., Ltd.), and the molecular weight and molecular weight of the resin. The distribution was measured using GPC (Gel Permeation Chromatography) (trade name: HLC-8220GPC; Tosoh Corporation). (Co., Ltd.).

(Preparation of polymer dispersant A)
[Synthesis of AB type diblock copolymer]
After replacing the inside of the glass container fitted with the three-way cock with nitrogen, the adsorbed water was removed by heating at 250 ° C. in a nitrogen gas atmosphere. After returning the system to room temperature, the atmosphere was changed to a nitrogen gas atmosphere, and 12 mmol of isobutyl vinyl ether, 16 mmol of ethyl acetate, 0.1 mmol of 1-isobutoxyethyl acetate, and 11 ml of toluene were added to adjust the system temperature to 0 ° C. Then, 0.2 mmol of ethylaluminum sesquichloride was added to initiate polymerization, and an A block of AB type diblock polymer was synthesized.

The molecular weight was monitored in a time-sharing manner using GPC, and after the polymerization of the A block was completed, the polymerization was further carried out by adding 12 mmol of ethyl 4- [2-vinyloxyethoxy] benzoate serving as the B block. The polymerization reaction was stopped by adding methanol / weak base, and dichloromethane and a 0.6N aqueous hydrochloric acid solution were added to the solution and stirred to separate and extract into the organic layer. Thereafter, the organic layer was concentrated and dried to obtain an AB type diblock copolymer. The compound was identified using NMR and GPC (Mn = 3.5 × 10 ⁴ , Mw / Mn = 1.2, Mn; number average molecular weight, Mw; weight average molecular weight, Mw / Mn is molecular weight distribution) Indicating the degree of).

  By hydrolyzing the B block with sodium hydroxide, the side chain terminal becomes a hydrophilic block of carboxylic acid, and an AB type diblock copolymer (polymer dispersing agent A comprising a hydrophobic block and a hydrophilic block) )

Example 1
C. of oil-soluble dyes I. 10 parts of Solvent Yellow 62 and 1 part of N, N-dimethylformamide were mixed and kneaded for 2 hours using a roll mill. Thereafter, this mixture was transferred to a beaker, 10 parts of the above polymeric dispersant A and 100 parts of ion exchange water were added, and ultrasonic treatment was performed for 3 hours to obtain an aqueous color material dispersion Y-1.

In evaluating the obtained dispersion, a water-based ink was prepared.
Aqueous colorant dispersion Y-1 50 parts Diethylene glycol 20 parts Acetylenol EH (nonionic surfactant)
0.15 parts / amount of ion-exchanged water to be 100 parts After mixing at the above ratio and stirring for 1 hour, the aqueous ink obtained was filtered under reduced pressure using a 3 μm membrane filter [manufactured by Toyo Roshi Kaisha, Ltd.] A water-based ink was prepared.

Example 2
C. I. Instead of Solvent Yellow 62, C.I. I. A water-based color material dispersion R-1 and a water-based ink were obtained in the same manner as in Example 1 except that Solvent Red 24 was used.

Example 3
C. I. Instead of Solvent Yellow 62, C.I. I. Pigment Red 122 was used, and N, N-dimethylformamide was replaced with N, N-dimethylacetamide, and the others were the same as in Example 1 to obtain an aqueous color material dispersion R-2 and an aqueous ink.

Example 4
C. I. Instead of Solvent Yellow 62, C.I. I. A water-based color material dispersion B-2 and a water-based ink were obtained in the same manner as in Example 1 except that Vat Blue 6 was used.

Example 5
C. I. Instead of Solvent Yellow 62, C.I. I. Pigment Blue 15: 3 was used, and N, N-dimethylformamide was replaced with hexamethylphosphoric triamide, and the other procedures were followed in the same manner as in Example 1 to obtain an aqueous color material dispersion B-3 and an aqueous ink.

Comparative Example 1
C. of oil-soluble dyes I. 10 parts of Solvent Yellow 62 and 1 part of N, N-dimethylformamide were mixed and kneaded for 2 hours using a roll mill. Thereafter, the mixture was transferred to a beaker, and 10 parts of a commercially available styrene-maleic acid copolymer (Mn = 3.5 × 10 ⁴ ) and 100 parts of ion-exchanged water were added and subjected to ultrasonic treatment for 3 hours to obtain an aqueous coloring material. Dispersion Y-x was obtained. In evaluating the obtained dispersion, a water-based ink was prepared.

Aqueous colorant dispersion Yx 50 parts Diethylene glycol 20 parts Acetylenol EH 0.15 parts Ion exchange water Total amount of 100 parts After mixing for 1 hour and stirring for 1 hour, the resulting aqueous ink Vacuum filtration was performed using a 3 μm membrane filter (manufactured by Toyo Roshi Kaisha, Ltd.) to prepare a water-based ink.

Comparative Example 2
C. I. Instead of Solvent Yellow 62, C.I. I. A water-based color material dispersion R-x1 and a water-based ink were obtained in the same manner as in Comparative Example 1 except that Solvent Red 24 was used.

Comparative Example 3
C. I. Instead of Solvent Yellow 62, C.I. I. Pigment Red 122 was used, and N, N-dimethylformamide was replaced with N, N-dimethylacetamide, and a water colorant dispersion R-x2 and a water-based ink were obtained in the same manner as in Comparative Example 1.

Comparative Example 4
C. I. Instead of Solvent Yellow 62, C.I. I. Pigment Red 122 was used, and an aprotic polar solvent was not used at all. In the same manner as in Comparative Example 1, an aqueous color material dispersion R-x3 and an aqueous ink were obtained.

Comparative Example 5
C. I. Instead of Solvent Yellow 62, C.I. I. A water-based color material dispersion B-x1 and a water-based ink were obtained in the same manner as in Comparative Example 1 except that Vat Blue 6 was used.

Comparative Example 6
C. I. Instead of Solvent Yellow 62, C.I. I. In the same manner as in Comparative Example 1 except that CI Pigment Blue 15: 3 was used, an aqueous color material dispersion B-x2 and an aqueous ink were obtained.

The aqueous inks obtained in the above examples and comparative examples were applied to paper and then evaluated by the following methods.
Hue: Compared with Examples and Comparative Examples with the same coloring material, hues (◎) that are superior to those of the comparative examples (◎), those that are almost the same (○), those that are below (×) It was.
Particle diameter: The diameter of dispersed particles in the ink was measured by a light scattering method.
Dispersion stability: Place water-based ink in a test tube and leave it to stand. Visually check the state of precipitate formation after 1 week. No precipitate (○), trace amount of precipitate (△), large amount of precipitate (×). Evaluation was made in three stages.
The results are as shown in Table 1.

(Preparation of polymer dispersant B)
[Synthesis of ABC type triblock copolymer]
After replacing the inside of the glass container fitted with the three-way cock with nitrogen, the adsorbed water was removed by heating at 250 ° C. in a nitrogen gas atmosphere. After returning the system to room temperature, 1-isobutyl vinyl ether, ethyl acetate, 1-isobutoxyethyl acetate and toluene were added, and when the internal temperature reached 0 ° C., ethyl aluminum sesquichloride was added to initiate polymerization. A component of the block copolymer was synthesized. The molecular weight is monitored in a time-sharing manner using GPC, and after the polymerization of component A is completed, synthesis is performed by adding 2-methoxyethyl vinyl ether as component B, and monitoring is performed using GPC as described above. Completion of polymerization of component B was confirmed.

Next, synthesis was carried out by adding ethyl 4- [2-vinyloxyethoxy] benzoate as component C, and the polymerization reaction was stopped by adding a 0.3% ammonia / methanol solution in the system. In order to identify the obtained triblock copolymer, NMR and GPC were used, and the result which showed that the target substance was synthesize | combined was obtained. The number average molecular weight (Mn) was 40,000, and the weight average molecular weight (Mw) / number average molecular weight ratio (Mw / Mn) indicating the degree of molecular weight distribution was 1.2.
The triblock copolymer was hydrolyzed with sodium hydroxide, whereby a side chain terminal became a hydrophilic block of carboxylic acid, and a polymer dispersant B was obtained.

Example 6
An aqueous ink was obtained in the same manner as in Example 1 except that the polymer dispersant B was used in place of the polymer dispersant A, and N, N-dimethyl sulfoxide was used as the aprotic polar solvent. The water-based ink had excellent dispersion stability as in Example 1.

(Preparation of polymer dispersant C)
[Synthesis of AB type diblock copolymer]
12 mmol of isobutyl vinyl ether was used as the hydrophobic monomer, 12 mmol of 2-methoxyethyl vinyl ether was used as the hydrophilic monomer, and the AB type diblock copolymer (polymer dispersant C) was used in the same manner as polymer dispersant A. )
The number average molecular weight (Mn) of the obtained diblock copolymer is 25,000 in terms of standard polystyrene, and the weight average molecular weight (Mw) / number average molecular weight ratio (Mw / Mn) indicating the degree of molecular weight distribution is 1.3. Met.

Example 7
A water-based ink was obtained in the same manner as in Example 1 except that the polymer dispersant C was used in place of the polymer dispersant A, and N, N-dimethylacetamide was used as the aprotic polar solvent. The water-based ink had excellent dispersion stability as in Example 1.

(Preparation of polymer dispersant D)
[Synthesis of AB type diblock copolymer]
12 mmol of 2-decanoxyethyl vinyl ether is used as the hydrophobic monomer, 12 mmol of 4- [2-vinyloxyethoxy] ethyl benzoate is used as the hydrophilic monomer, and the others are the same as in Polymer Dispersant A. AB type diblock copolymer was obtained. In addition, the ester part of the B component of these diblock copolymers was hydrolyzed using an aqueous sodium hydroxide solution to obtain a polymer dispersant D having a carboxylic acid type at the side chain end.
The number average molecular weight of the obtained diblock copolymer was 3,5000 in terms of standard polystyrene, and the weight average molecular weight (Mw) / number average molecular weight ratio (Mw / Mn) indicating the degree of molecular weight distribution was 1.2. .

Example 8
A water-based ink was obtained in the same manner as in Example 1 except that the polymer dispersant D was used in place of the polymer dispersant A and acetonitrile was used as the aprotic polar solvent. The water-based ink had excellent dispersion stability as in Example 1.

(Preparation of polymer dispersant E)
[Synthesis of AB type diblock copolymer]
12 mmol of isobutyl vinyl ether is used as the hydrophobic monomer, 12 mmol of vinyl monomer obtained by silylation of the hydroxyl group of 2-hydroxyethyl vinyl ether with trimethylchlorosilane is used as the hydrophilic monomer, and the other is the AB type dimer in the same manner as the polymer dispersant A. A block copolymer (polymer dispersant E) was obtained.
The number average molecular weight of the obtained triblock copolymer was 3,7000 in terms of standard polystyrene, and the weight average molecular weight (Mw) / number average molecular weight ratio (Mw / Mn) indicating the degree of molecular weight distribution was 1.3. .

Example 9
A water-based ink was obtained in the same manner as in Example 1 except that the polymer dispersant E was used in place of the polymer dispersant A, and hexamethylphosphoric triamide was used as the aprotic polar solvent. The water-based ink had excellent dispersion stability as in Example 1.

Inkjet suitability (dischargeability):
Each of the inks of the examples and comparative examples is mounted on an ink-jet recording apparatus BJF-660 (manufactured by Canon) having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to a recording signal to the ink. did. A 100% solid image was printed on Canon glossy paper SP101 at 5 ° C in an environment with a relative humidity of 10%, and after resting for 1 minute, the image on which the 100% solid image was printed again was evaluated according to the following evaluation criteria. did.
(Double-circle): There is no white stripe and it is printed normally.
○: Slight white streaks are observed at the beginning of printing.
Δ: White streaks are observed in the entire image.
X: An image is hardly printed.
The evaluation results are shown in Table 2.

As described above, according to the present invention, it is possible to obtain a water-based ink excellent in color reproducibility and storage stability in a color material particle-dispersed ink.

Claims (5)

  A color material dispersion in which capsule particles whose surfaces of color material particles are coated with a resin are dispersed in an aqueous medium, wherein the resin includes at least one hydrophilic block and at least one hydrophobic block. A water-based colorant dispersion characterized in that an organic solvent is present in the capsule.   The aqueous color material dispersion according to claim 1, wherein the organic solvent is an aprotic polar solvent.   The aqueous color material dispersion according to claim 1 or 2, wherein the block copolymer is a block copolymer having a polyvinyl ether structure.   The aqueous color material dispersion according to claim 1, wherein the color material is a water-insoluble color material. An ink-jet ink comprising the aqueous color material dispersion according to claim 1 as a colorant.