JP2008019399A - Inkjet ink colorant and inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink colorant being small in primary particle diameters and uniform in particle sizes, having a high coloring power and high dispersibility, and excellent weather resistance, and to provide an inkjet ink containing the inkjet colorant and being excellent in dispersion stability and weather resistance. <P>SOLUTION: Provided are an inkjet ink colorant comprising fine composite particles comprising an organic pigment and 0.001-9 wt.% silica (in terms of Si) entrapped therein, and an inkjet ink containing the colorant. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a colorant for an inkjet ink having a small primary particle size, a uniform particle size, high coloring power, excellent dispersibility, and excellent weather resistance, and the inkjet It is an object of the present invention to provide an ink-jet ink excellent in dispersibility, dispersion stability and weather resistance, which contains a coloring material for an ink.

  Various office automation equipment such as personal computers are rapidly spreading regardless of whether they are for business use or home use, and inkjet printers, which are one of the recording devices, have also become widespread due to recent price reductions and quality improvements. I am doing.

  In recent years, inkjet printers have achieved high-definition and high-gloss image quality levels similar to those of silver halide photographs, and as a result, printed materials have been used for a variety of purposes. ) Has come to be emphasized.

  Conventionally, dyes have been used as coloring materials for ink-jet inks in terms of clogging of the head portion, ink dispersion stability, saturation, etc., but dyes have toxicity problems, and recent printed matter In order to improve the weather resistance, attempts have been made to make pigments into inks as colorants against dyes.

  However, when a pigment is used as a colorant for an ink jet ink, the density of the printed image is higher than that when a dye is used as the colorant and the weather resistance is excellent. In general, 80% of the constituent components of ink are water, and it is particularly difficult to disperse organic pigments, which are organic substances. In addition, unlike a dye, a pigment is insoluble in a solvent such as water, so that it is difficult to keep inkjet ink stable for a long period of time, and the head portion is likely to be clogged. . In addition, organic pigments form fine primary particles of about 20 nm to 100 nm from a pigment in a molecular state by a chemical reaction or the like, but in this state, the surface energy of the particles is so high that the particles are likely to agglomerate and have a particle size of It was difficult to make uniform and it was difficult to obtain a clear image without dullness.

  On the other hand, it can be expected that the clogging of the head portion will be reduced by reducing the particle size of the colorant, but on the other hand, there is a problem that dispersion in the ink composition becomes difficult and the weather resistance is lowered. .

  So far, for the purpose of obtaining a high-quality printed image, an aqueous inkjet recording liquid containing a pigment and colloidal silica (Patent Documents 1 and 2) has been proposed.

  In addition, as a coloring material that is fine and excellent in light resistance, an average particle diameter of 0.001 to 0 in which the particle surface of the extender pigment is coated with a paste and the organic pigment forms a uniform adhesion layer on the coating Inkjet ink colorants (Patent Documents 3 to 6) made of .15 μm composite particle powder have been proposed.

  In addition, as a fine colorant having excellent transparency, the entire amount of white inorganic particles as core particles can be dissolved in composite particles in which organic pigments are attached to the surface of white inorganic particles via a paste material such as alkoxysilane. There has been proposed a colored fine particle powder (Patent Document 7) in which core particles are completely dissolved and removed using an acid or alkali equal to or more than a theoretical value.

JP-A-9-227812 JP 2000-53901 A JP 2003-55591 A JP 2003-268278 A JP 2003-327880 A JP 2006-111875 A JP 2003-246941 A

  At present, an ink-jet ink coloring material having a small primary particle size, a uniform particle size, and high coloring power and excellent weather resistance is most demanded. However, in order to obtain a high coloring power, it is necessary to make the pigment finer. However, since the weather resistance tends to decrease as the particle diameter of the pigment decreases, the colorant that satisfies these contradicting characteristics is: It has not been obtained yet.

  That is, Patent Documents 1 and 2 describe an aqueous inkjet recording liquid containing a pigment and colloidal silica. However, since the ζ potential of the organic pigment itself is close to zero, an electrostatic repulsion effect in the vehicle is obtained. Therefore, it is difficult to obtain good dispersibility and dispersion stability in the vehicle. Further, since a large amount of colloidal silica not involved in coloring is added, the pigment concentration cannot be increased, which is disadvantageous for increasing the density of a printed image.

  Further, Patent Document 3 discloses composite particles having an average particle diameter of 0.001 to 0.15 μm, in which the particle surface of the extender pigment is coated with a paste and the organic pigment forms a uniform adhesion layer on the coating. Although powder is described, as shown in the comparative example described later, since white inorganic particle powder such as silica particles is used as the core particle, high coloring power equal to or higher than the raw material organic pigment to be attached can be easily obtained. It was difficult to get.

  Further, Patent Document 4 discloses a theoretical equivalent amount or more that can dissolve all of the white inorganic particles as the core particles with respect to the composite particles in which the organic pigment is attached to the surface of the white inorganic particles through a paste material such as alkoxysilane. The method of completely dissolving and removing the core particles using an acid or alkali to leave the organic pigment is described. However, as shown in the comparative example, the organic pigment is used because the acid or alkali is used in an amount equal to or more than the theoretical value. It is difficult to obtain a colorant with good light resistance. In addition, since silica is completely dissolved and removed, the ζ potential is close to zero, and it is difficult to obtain an electrostatic repulsion effect in the vehicle. Therefore, it is difficult to obtain good dispersibility and dispersion stability in the vehicle. Become.

  Accordingly, an object of the present invention is to provide an ink-jet ink coloring material having a small primary particle size, a uniform particle size, and high coloring power and excellent weather resistance.

  The technical problem can be achieved by the present invention as follows.

  That is, the present invention is an ink-jet ink colorant comprising fine composite particles in which silica is encapsulated in an organic pigment (Invention 1).

  Further, according to the present invention, the silica contained in the fine composite particles is 0.001 to 9% by weight in terms of Si with respect to the fine composite particle powder. It is a coloring material. (Invention 2).

  In addition, the present invention is an ink-jet ink containing the ink-jet ink coloring material according to the first or second aspect of the present invention (Invention 3).

  The colorant of the inkjet ink according to the present invention has a small primary particle size, a uniform particle size, high coloring power, excellent dispersibility, and excellent weather resistance. Therefore, it is suitable as a coloring material for inkjet ink.

  The ink-jet ink according to the present invention is suitable as an ink-jet ink excellent in dispersibility, dispersion stability, and weather resistance because the fine composite particles having the above characteristics are used as a coloring material for the ink-jet ink.

  Hereinafter, the coloring material of the ink-jet ink according to the present invention will be described.

  The colorant of the ink jet ink according to the present invention is composed of fine composite particles in which silica is included in an organic pigment.

  The amount of silica contained in the colorant of the inkjet ink according to the present invention is 0.001 to 9.0% by weight, more preferably 0.005 to 7%, based on the colorant of the inkjet ink, in terms of Si. 0.0% by weight, most preferably 0.01-5.0% by weight. When the amount of silica is less than 0.001% by weight in terms of Si with respect to the colorant of the ink jet ink, the amount of silica contained in the colorant of the ink jet ink is too small. Since the ζ potential is almost zero and an electrostatic repulsion effect cannot be obtained, dispersibility in the vehicle is deteriorated. Further, since there is almost no silica, it is difficult to obtain sufficient weather resistance. On the other hand, if it exceeds 9.0% by weight, it is difficult to obtain sufficient coloring power because the amount of silica contained in the coloring material of the inkjet ink is too large.

  The average primary particle diameter of the coloring material of the ink jet ink according to the present invention is preferably 1 to 50 nm, more preferably 1 to 40 nm, and most preferably 1 to 30 nm.

  The particle size distribution of the primary particles of the colorant of the colorant of the inkjet ink according to the present invention is preferably 2.0 or less, more preferably 1.8 or less, and still more preferably as the geometric standard deviation value of the particle size of the primary particles. 1.5 or less. If it exceeds 2.0, the particle size distribution of the composite pigment is wide, and the dispersibility and dispersion stability in the ink jet ink are lowered, which is not preferable.

  The average particle diameter in terms of the number of the coloring material of the inkjet ink according to the present invention is preferably 150 nm or less, more preferably 1 to 100 nm, still more preferably 1 to 50 nm, and most preferably 1 to 40 nm. When the average particle diameter in terms of the number of colorants of the inkjet ink exceeds 150 nm, the particle size is too large, and the inkjet ink obtained using this suppresses clogging of the head portion of the inkjet recording apparatus. Since it becomes difficult to do, it is not preferable.

  The average particle diameter in terms of volume of the coloring material of the inkjet ink according to the present invention is preferably 1 to 150 nm, more preferably 1 to 125 nm, and still more preferably 1 to 100 nm. When the volume-converted average particle diameter of the coloring material of the inkjet ink exceeds 150 nm, the particle size is too large, and the inkjet ink obtained using this suppresses clogging of the head portion of the inkjet recording apparatus. Since it becomes difficult to do, it is not preferable.

BET specific surface area value of colorant of the inkjet ink according to the present invention is preferably from 20 to 500 m ² / g, more preferably 25~400m ² / g, still more preferably 30~300m ² / g. When the BET specific surface area value is less than 20 m ² / g, the particles are coarse and the coloring power is reduced.

  The coloring power of the coloring material of the inkjet ink according to the present invention is preferably 102% or more, more preferably 103% or more, and still more preferably 104% or more according to an evaluation method described later.

In the evaluation method described later, the light resistance of the coloring material of the inkjet ink according to the present invention is preferably 5.0 or less, more preferably 4.5 or less, and still more preferably 4.E ^* value. 0 or less. When the ΔE ^* value exceeds 5.0, the printed matter printed with the ink jet ink using this as a coloring material does not have sufficient weather resistance.

  The ζ potential of the colorant of the inkjet ink according to the present invention is preferably −5 mV or less, more preferably −8 mV or less, and further preferably −10 mV or less. When the ζ potential is closer to zero than −5 mV, it is difficult to obtain good dispersibility and dispersion stability due to the electrostatic repulsion effect.

  Next, the inkjet ink containing the inkjet ink coloring material according to the present invention will be described.

  The ink-jet ink according to the present invention comprises a colorant, a dispersant and water of the ink-jet ink, and if necessary, a water-soluble resin, a penetrating agent, a humectant, a water-soluble solvent, a pH adjuster, a preservative and the like It may contain.

  The ratio of the coloring material in the ink jet ink is preferably 1 to 20% by weight with respect to the ink constituent solution.

  The proportion of the dispersant in the inkjet ink is preferably 5 to 200% by weight, more preferably 7.5 to 150% by weight, and most preferably 10 to 100% by weight with respect to the colorant of the inkjet ink.

  As the dispersant, a surfactant and / or a polymer dispersant can be used. Considering the dispersibility and dispersion stability of the colorant in the ink jet ink, the surfactant is preferably an anionic surfactant or nonionic surfactant, and the polymer dispersant is a styrene-acrylic acid copolymer. A water-soluble resin such as a polymer is preferred.

  Specifically, as the anionic surfactant, specifically, fatty acid salt, sulfate ester salt, sulfonate salt, phosphate ester salt and the like can be used, more preferably sulfate ester salt and sulfonate salt. It is. The

  Specific examples of nonionic surfactants include polyethylene glycol type nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene aryl ether, polyhydric alcohol type nonionic surfactants such as sorbitan fatty acid ester, etc. More preferably, it is a polyethylene glycol type nonionic surfactant.

  Specific examples of the cationic surfactant include amine salt type cationic surfactants and quaternary ammonium salt type cationic surfactants, and more preferably quaternary ammonium salt type cations. It is a system surfactant.

  As the polymer dispersant, an alkali-soluble resin such as a styrene-acrylic acid copolymer, a styrene-maleic acid copolymer, or a polyacrylic acid derivative can be used.

  The ink-jet ink according to the present invention can use water as a solvent and, if necessary, a water-soluble organic solvent. The ratio of the water-soluble organic solvent in the inkjet ink is preferably 1 to 50% by weight, more preferably 1 to 40% by weight, and most preferably 1 to 30% by weight with respect to the ink constituent solution.

  Water-soluble organic solvents include monohydric alcohols such as methanol, ethanol, n-propanol, iso-propanol, and butanol, and dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, and dipropylene glycol. Trialkyl alcohols such as glycerin, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, lower alkyl ethers of polyhydric alcohols such as diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoethyl ether, etc. They may be used alone or in combination.

  The number-average dispersion average particle diameter of the inkjet ink according to the present invention is preferably 1 to 150 nm, more preferably 1 to 100 nm, still more preferably 1 to 50 nm, and most preferably 1 to 40 nm. When the number-converted dispersed particle diameter exceeds 150 nm, the head portion is likely to be clogged, and the dispersion stability of the coloring material in the inkjet ink is lowered.

  The volume conversion average particle diameter of the ink-jet ink according to the present invention is preferably 1 to 150 nm, more preferably 1 to 125 nm, and still more preferably 1 to 100 nm. When the volume-converted dispersed particle diameter exceeds 150 nm, the head portion is likely to be clogged, and the dispersion stability of the coloring material in the inkjet ink is lowered.

  The dispersion stability of the inkjet ink according to the present invention is preferably 5 or 4 and more preferably 5 in visual observation in a later evaluation method. Further, the change rate of the number converted dispersed particle diameter is preferably 10% or less, more preferably 8% or less.

The specific extinction coefficient ε _w (weight basis) representing the coloring power of the inkjet ink according to the present invention is preferably 1.20 or more, more preferably 1.40 to 5.00, by an evaluation method described later. Yes, more preferably 1.50 to 5.00.

The weather resistance of a printed image obtained using the inkjet ink according to the present invention is preferably 3.0 or less, more preferably 2.5 or less, and most preferably 2.0 or less in terms of ΔE ^* value.

  The clogging resistance of the head portion of the ink-jet ink according to the present invention is preferably 5 or 4 and more preferably 5 in visual observation in the later evaluation method.

  Next, a method for producing a coloring material for ink-jet ink according to the present invention is described.

  The colorant of the ink-jet ink according to the present invention is obtained by mixing and stirring silica particles as a core particle and a surface modifier, coating the surface modifier on the particle surface of the silica particles, adding an organic pigment, and mixing After stirring to obtain composite particles in which an organic pigment is attached to the surface of the silica particles coated with the surface modifier, the silica particles and the surface modifier of the composite particles are mixed using an alkaline solution. It can be obtained by dissolving a part.

  The average primary particle diameter of the silica particles in the present invention is preferably 1 to 100 nm, more preferably 1 to 75 nm, and most preferably 1 to 50 nm.

BET specific surface area value of the silica particles in the invention is preferably from 10 to 1000 m ² / g, more preferably 15~500m ² / g.

  As the surface modifier in the present invention, anything may be used as long as an organic pigment can be attached to the surface of the silica particles, and an organosilicon compound such as alkoxysilane, silane coupling agent and organopolysiloxane, Coupling agents such as titanate-based, aluminate-based and zirconate-based, low-molecular or high-molecular surfactants and the like are preferably used. More preferred are organosilane compounds such as alkoxysilanes, silane coupling agents and organopolysiloxanes.

  Examples of organosilicon compounds include methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, ethyltriethoxysilane, propyl Alkoxysilanes such as triethoxysilane, butyltriethoxysilane, isobutyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane and decyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane , Γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloyloxypropyltrime Silane coupling agents such as xylsilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, polysiloxane, methylhydrogen And organopolysiloxanes such as polysiloxane and modified polysiloxane.

  Titanate coupling agents include isopropyl tristearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl / aminoethyl) titanate, tetraoctyl bis (ditridecyl phosphate titanate, tetra (2,2 diallyl) Examples include oxymethyl-1-butyl) bis (ditridecyl) phosphate titanate, bis (dioctylpyrophosphate) oxyacetate titanate, and bis (dioctylpyrophosphate) ethylene titanate.

  Examples of the aluminate coupling agent include acetoalkoxy aluminum diisopropylate, aluminum diisopropoxy monoethyl acetoacetate, aluminum trisethyl acetoacetate, aluminum trisacetylacetonate and the like.

  Examples of the zirconate coupling agent include zirconium tetrakisacetylacetonate, zirconium dibutoxybisacetylacetonate, zirconium tetrakisethylacetoacetate, zirconium tribotoxymonoethylacetoacetate, zirconium tributoxyacetylacetonate and the like.

  Examples of the low molecular surfactant include alkylbenzene sulfonate, dioctyl sulfone succinate, alkylamine acetate, alkyl fatty acid salt and the like. Examples of the polymeric surfactant include polyvinyl alcohol, polyacrylate, carboxymethylcellulose, acrylic acid-maleate copolymer, and olefin-maleate copolymer.

  The coating amount of the surface modifier is preferably 0.05 to 15.0% by weight, more preferably 0.1 to 12.0% by weight, and still more preferably, in terms of C with respect to the silica particles as the core particles. 0.15 to 10.0% by weight. By setting it as 0.05-15 weight%, 10-500 weight part of organic pigments can be made to adhere with respect to 100 weight part of silica particles.

  As the organic pigment in the present invention, in general, red organic pigments, blue organic pigments, yellow organic pigments, green organic pigments, which are used as coloring materials for printing inks, inkjet inks, toners, color filters, and the like, Various organic pigment particle powders such as orange organic pigments, brown organic pigments and purple organic pigments can be used. However, organic pigments with weak alkali resistance, such as alkali blue and isoindoline organic pigments, are used in the present invention because the organic pigment contained in the composite particles dissolves when the silica particles are alkali-dissolved by the method described below. It is not preferable to use the fine composite particle powder according to the above.

  Among various organic pigments, red organic pigments include azo pigments such as brilliant carmine, permanent red, and condensed azo red, and diaminoanthraquinonyl red, quinacridone red, thioindigo red, perylene red, perinone red, and diketopyrrolopyrrole. Although condensed polycyclic pigments such as red can be used, quinacridone pigments such as quinacridone red are preferred in consideration of weather resistance. As the blue organic pigment, phthalocyanine pigments such as metal-free phthalocyanine blue, phthalocyanine blue and fast sky blue, and condensed polycyclic pigments such as indanthrone blue and indigo blue can be used. As yellow organic pigments, azo pigments such as Hansa Yellow, Benzidine Yellow, Permanent Yellow, and condensed azo yellow, and condensed polycyclic pigments such as isoindolinone yellow, anthrapyrimidine yellow, and quinophthalone yellow can be used. As the green pigment, a phthalocyanine pigment such as phthalocyanine green can be used.

  In addition, as the orange organic pigment, an azo pigment such as permanent orange, resol fast orange, pyrazolone orange, balkan fast orange, or a condensed polycyclic pigment such as quinacridone, perinone orange, or diketopyrrolopyrrole orange may be used. it can. As the brown organic pigment, azo pigments such as permanent brown, para brown and benzimidazolone brown and condensed polycyclic pigments such as thioindigo brown can be used. As the purple organic pigment, azo pigments such as fast violet and condensed polycyclic pigments such as unsubstituted quinacridone, dioxazine violet and perylene violet can be used. The organic pigment used in the present invention is not limited to the pigments exemplified above.

  In addition, you may mix and use each said organic pigment according to the hue requested | required. Further, two or more kinds of similar colors may be used according to the required hue and characteristics.

  The addition amount of the organic pigment is 10 to 500 parts by weight, preferably 30 to 400 parts by weight, and more preferably 50 to 300 parts by weight with respect to 100 parts by weight of the silica particles as the core particles.

  In the composite particles in the present invention, silica particles and a surface modifier are mixed, the particle surfaces of the silica particles are coated with the surface modifier, and then the silica coated with the surface modifier and the organic pigment are mixed. Can be obtained. Almost all of the added surface modifier is coated on the silica surface.

  As a device for mixing and stirring silica particles and a surface modifier, and mixing and stirring organic pigments and silica particles whose surface is coated with a surface modifier, a shear force can be applied to the powder layer. An apparatus is preferable, and in particular, an apparatus capable of simultaneously performing shearing, spatula and compression, for example, a wheel-type kneading machine, a ball-type kneading machine, a blade-type kneading machine, a roll-type kneading can be used, and a wheel The mold kneader can be used more effectively.

  Examples of the wheel type kneader include edge runners (synonymous with “mix muller”, “simpson mill”, “sand mill”), multi-mal, stotz mill, wet pan mill, conner mill, ring muller, etc. Are edge runners, multi-mals, stocks mills, wet pan mills, ring mullers, more preferably edge runners. Examples of the ball kneader include a vibration mill. Examples of the blade-type kneader include a Henschel mixer, a planetary mixer, and a nauter mixer. Examples of the roll-type kneader include an extruder.

  After the surface of the silica particles is coated with a surface modifier, an organic pigment is added, mixed and stirred to adhere the organic pigment to the surface of the surface modifier-coated silica particles. At this time, drying or heat treatment may be performed as necessary. The organic pigment is added little by little while taking a time of about 5 minutes to 24 hours, preferably about 5 minutes to 20 hours, or 5 to 25 parts by weight of the organic pigment with respect to 100 parts by weight of silica particles, It is preferable to divide and add until a desired addition amount is obtained.

  After attaching an organic pigment to the surface modifier-coated silica particle surface, drying or heat treatment may be further performed as necessary. In the case of performing drying or heat treatment, the heating temperature is usually preferably 40 to 80 ° C, more preferably 50 to 70 ° C, and the heating time is preferably 10 minutes to 6 hours, more preferably 30 minutes to 3 hours. .

  The average particle diameter of the primary particles of the obtained composite particles is 1 to 100 nm, more preferably 1 to 50 nm, and still more preferably 1 to 30 nm.

BET specific surface area value of the composite particles is preferably from 10 to 500 m ² / g, more preferably 15~400m ² / g, still more preferably 20 to 300 m ² / g.

  The degree of detachment of the organic pigment from the composite particles is preferably 4 or 3 and more preferably 4 in visual observation in the later evaluation method. When the degree of desorption of the organic pigment is 2 or less, since the desorbed organic pigment is coarsened by causing recrystallization or aggregation or the like, it is mixed in the fine composite particle powder as the final product. It is not preferable.

  The coloring material of the inkjet ink according to the present invention can be obtained by treating the composite particles with an alkali and dissolving silica or silica and a surface modifier so that a part of the silica component remains.

  As the alkali used for dissolution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, ammonia, or the like can be used.

  The composite particle concentration in the solution at the time of the dissolution treatment is preferably 1.0 to 30.0 parts by weight, more preferably 2.5 to 25.0 parts by weight, still more preferably 5. 0 to 20.0 parts by weight.

  The alkali amount of the solution when the silica particles in the composite particles or the silica particles and the surface modifier are dissolved is 0 of the alkali amount necessary for dissolving the silica particles or the silica particles and the surface modifier in its entirety. 0.01 to 0.95 times are preferable, 0.02 to 0.90 times are more preferable, and 0.05 to 0.85 times are more preferable. When treated with an alkali amount exceeding 0.95 times, the silica particles or the silica particles and the surface modifier are completely dissolved, so that it is not possible to obtain the ink-jet ink coloring material of the present invention. . When the amount of alkali is less than 0.01 times, the silica particles or the silica particles and the surface modifier are industrially used because it takes a very long time to dissolve up to 9% by weight or less with respect to the coloring material of the inkjet ink. Is not preferable.

  The pH when the silica particles in the composite particles or the silica particles and the surface modifier are dissolved is preferably 10.0 to 13.8, more preferably 11.0 to 13.6, and still more preferably 11. .5 to 13.4. When the pH exceeds 13.8, damage to the organic pigment due to alkali increases, and it is difficult to obtain a colorant for inkjet ink having good weather resistance. When the pH is less than 10.0, it takes a very long time to dissolve the silica particles or the silica particles in the composite particles and the surface modifier to 9% by weight or less with respect to the colorant of the ink jet ink. Industrially unfavorable.

  40-100 degreeC is preferable, as for the process temperature at the time of performing a melt | dissolution process, More preferably, it is 45-90 degreeC, More preferably, it is 50-80 degreeC. When the temperature is lower than 40 ° C., it takes a long time exceeding 50 hours to dissolve the silica, which is industrially disadvantageous. When the temperature exceeds 100 ° C., it is difficult to obtain a coloring material for inkjet ink having good weather resistance due to damage to the organic pigment, and an apparatus such as an autoclave is required, which is not industrially preferable. .

  The treatment time for performing the dissolution treatment is preferably 5 minutes to 50 hours, more preferably 10 minutes to 30 hours, and even more preferably 20 minutes to 10 hours. When the treatment time is longer than 50 hours, it is industrially unfavorable because a long-time dissolution treatment is required.

  After the dissolution treatment, the solid content and the solution can be separated by filtration, washed, and then taken out using a normal drying or freeze-drying method. The coloring material of the ink jet ink obtained in the present invention is easily dispersible due to the electrostatic repulsion effect of silica or silica and a surface modifier even when subjected to normal drying.

  Next, a method for producing an ink jet ink according to the present invention will be described.

  The ink-jet ink according to the present invention includes a predetermined amount of a coloring material, a dispersant and water of the ink-jet ink according to the present invention, and if necessary, a penetrant, a humectant, a water-soluble solvent, a pH adjuster, a preservative, It is obtained by mixing and dispersing the agent with a disperser to prepare a primary dispersion, further adding and mixing water, a water-soluble solvent and other additives, followed by filtration using a membrane filter. .

  As the disperser, a ball mill, a sand mill, an attritor, a roll mill, a bead mill, a colloid mill, a two or three roll mill, an ultrasonic homogenizer, a high pressure homogenizer, and the like can be used.

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In the present invention, the most important point is that the colorant of the ink-jet ink according to the present invention has a fine primary particle size, a uniform particle size, and high coloring power and excellent dispersibility. And it is the fact that it is also excellent in weather resistance.

  Regarding the reason why the coloring material of the ink-jet ink according to the present invention has high coloring power and excellent dispersibility, in general, an organic pigment that has been simply miniaturized tends to cause aggregation because the surface energy of the particles is very high, and the vehicle Although it is difficult to maintain a fine particle state in the ink, the colorant of the ink jet ink according to the present invention has an absolute value of ζ potential because the silica is included in the organic pigment, so that it remains static in the vehicle. It is considered that an electric repulsion effect was obtained, and it could be dispersed in a fine state even in the vehicle, and a high coloring power could be obtained. In addition, the reason why the colorant of the ink-jet ink according to the present invention has excellent weather resistance is that the weather resistance is maintained even when the organic pigment is refined by including silica with high weather resistance in the organic pigment. In order to improve, this inventor presumes.

  The reason why the inkjet ink according to the present invention is excellent in dispersibility and dispersion stability is that the present inventor used silica for the organic pigment due to the use of the colorant of the inkjet ink according to the present invention. It is considered that the absolute value of the ζ potential is increased for inclusion, an electrostatic repulsion effect is obtained in the vehicle, and the dispersion and dispersibility can be maintained in a fine state even in the vehicle.

  Hereinafter, the present invention will be described in detail with reference to examples.

  The average primary particle size of each particle powder was measured by measuring the particle size of 350 particles shown in the electron micrograph, and the average particle size was indicated by the average value.

  The particle size distribution of the primary particle size of each particle powder was indicated by a geometric standard deviation value obtained by the following method.

  That is, the value obtained by measuring the particle diameter of the particles shown in the above electron micrograph is calculated on the horizontal axis on the log normal probability paper according to the statistical method from the actual particle diameter and the number of particles calculated from the measured value. The particle diameter is plotted on the vertical axis in terms of the cumulative number of particles belonging to each of the predetermined particle diameter sections (under integrated sieve) as a percentage. Then, from this graph, the particle diameter values corresponding to the number of particles of 50% and 84.13% are read, and the geometric standard deviation value = particle diameter under integrated fluid 84.13% / under integrated fluid 50%. The value was calculated according to the particle diameter (geometric mean diameter). The closer the geometric standard deviation value is to 1, the better the particle size distribution of the primary particles.

  The number-average particle size and the volume-average particle size of each particle powder are determined by dispersing an aqueous solution obtained by mixing the particle powder to be measured and water for 1 minute using an ultrasonic disperser, It was measured using a system particle size analyzer FPAR-1000 "(Otsuka Electronics Co., Ltd.).

  The specific surface area value was indicated by a value measured by the BET method.

  The coating amount of the surface modifier coated on the particle surface of the silica particles and the coating amount of the organic pigment adhering to the composite particle powder are “Horiba Metal Carbon / Sulfur Analyzer EMIA-2200 Model” (Horiba Co., Ltd.). It was determined by measuring the amount of carbon using a manufacturer).

  The amount of silica contained in the colorant of the ink jet ink was measured using a “fluorescence X-ray analyzer 3063M type” (manufactured by Rigaku Denki Kogyo Co., Ltd.) according to “General X-ray fluorescence analysis rules” of JIS K 0119. .

  The ζ potential of the coloring material of the ink-jet ink was adjusted so that the coloring material of the ink-jet ink had a concentration of 0.5 g / l using ion-exchanged water, and was dispersed for 3 minutes using an ultrasonic disperser. Then, it measured by the electrophoresis method using "Model501" (made by PEN KEN).

The hue of each particle powder is 0.5 g of a sample and 0.5 ml of castor oil, kneaded with a Hoover-type Mahler to form a paste. To this paste, 4.5 g of clear lacquer is added, kneaded and coated to form 150 μm on cast coated paper. An application piece (coating thickness: about 30 μm) applied using a (6 mil) applicator is prepared and measured using a “spectral colorimeter CM-3610d” (manufactured by Minolta Co., Ltd.). The color index is shown according to the definition. The C ^* value represents saturation and can be obtained according to the following formula 1.

<Equation 1>
C ^* value = ((a ^* value) ² + (b ^* value) ² ) ^1/2

The coloring power of each particle powder is as follows. First, each of the primary color enamel and the color development enamel prepared according to the method shown below is applied onto a cast coated paper using a 150 μm (6 mil) applicator to prepare a coated piece. The L ^* value was measured using a colorimeter CM-3610d (manufactured by Minolta Co., Ltd.), and the difference was taken as the ΔL ^* value.

Next, as a standard sample of the ink-jet ink colorant, using the organic pigment used when preparing the ink-jet ink colorant, a coating piece of primary color enamel and color-enameled enamel is produced in the same manner as described above. The L ^* value of each coated piece was measured and the difference was taken as the ΔLs ^* value.

The value calculated according to the following equation 2 using DerutaLs ^* value of [Delta] L ^* value and the standard sample of the coloring material of the ink-jet ink thus obtained are shown as the tinting strength (%).

<Equation 2>
Tinting strength (%) = 100 + {( ΔLs * value -Delta L ^* value) × 10}

Production of primary color enamel:
10g of the above sample powder, 16g of amino alkyd resin and 6g of thinner were mixed and added to a 140ml glass bottle together with 90g of 3mmφ glass beads. After mixing and dispersing for 45 minutes with a paint shaker, 50g of amino alkyd resin was added. Further, the primary color enamel was prepared by dispersing with a paint shaker for 5 minutes.

Production of color-enamel:
The primary color enamel (12 g) and amylac white (titanium dioxide-dispersed aminoalkyd resin) (80 g) were blended and mixed and dispersed for 15 minutes with a paint shaker to produce a color-enamel.

For the weather resistance of each particle powder, the primary color enamel prepared for measuring the coloring power described above was applied to a cold-rolled steel plate (0.8 mm x 70 mm x 150 mm) at a thickness of 150 µm and dried to form a coating film. Then, half of the obtained coating piece for measurement was covered with a metal foil, and “I Super UV Tester SUV-W13” (manufactured by Iwasaki Electric Co., Ltd.) was used for 6 hours continuously with an irradiation intensity of 100 mW / cm ^2. After the irradiation, the hue (L ^* value, a ^* value, b ^* value) of the portion not irradiated with ultraviolet rays and the portion irradiated with ultraviolet rays was measured by covering with a metal foil, and calculated according to the following formula 3. Indicated by ΔE ^* value.

<Equation 3>
ΔE ^* value = ((ΔL ^* value) ² + (Δa ^* value) ² + (Δb ^* value) ² ) ^1/2
ΔL ^* value: difference in L ^* value of sample to be compared with UV irradiation Δa ^* value: difference in a ^* value of sample to be compared with UV irradiation Δb ^* value: b ^* value of sample to be compared with UV irradiation difference

  The degree of detachment of the organic pigment adhering to the composite particles was evaluated in four stages by the following method. 4 indicates that the amount of the organic pigment released from the particle surface of the composite particle is small.

  2 g of particle powder to be measured and 20 ml of ethanol were placed in a 50 ml Erlenmeyer flask, subjected to ultrasonic dispersion for 60 minutes, and then centrifuged at 10,000 rpm for 15 minutes to separate the particle particle to be measured and the solvent part. . The obtained particle powder to be measured was dried at 80 ° C. for 1 hour, and the number of detached and re-aggregated organic pigment present in the field of view shown in the electron micrograph was visually observed and evaluated in four stages. .

1: 30 or more per 100 composite particles.
2: 10 or more and less than 30 per 100 composite particles.
3: 5 or more and less than 10 per 100 composite particles.
4: Less than 5 per 100 composite particles.

The coloring power of the inkjet ink is determined by putting an aqueous solution in which the concentration of the coloring material of the inkjet ink is adjusted to 0.08% by weight into a quartz cell, and calculating the extinction coefficient at the wavelength with the largest light absorption by referring to “Self-recorded photoelectric spectrophotometer UV”. -2100 "(manufactured by Shimadzu Corporation), and indicated by a specific extinction coefficient ε _w calculated according to the following formula 4. It shows that the coloring power of the dispersion containing the coloring material of inkjet ink is so high that the value of a specific extinction coefficient is large.

<Equation 4>
ε _w = ε _h / ε ₀
ε _w : Specific absorption coefficient ε _h : Absorption coefficient per unit weight of the coloring material of each inkjet ink ε ₀ : Absorption coefficient per unit weight of the organic pigment used as a raw material of the coloring material of each inkjet ink

The dispersion average particle diameter Dd ₅₀ , the dispersion particle diameter Dd ₈₄ and the dispersion maximum particle diameter Dd ₉₉ in the inkjet ink are determined using a dynamic light scattering method “Dense System Particle Size Analyzer FPAR-1000” (manufactured by Otsuka Electronics Co., Ltd.). Measured. The geometric standard deviation value (Dd ₈₄ / Dd ₅₀ ) is a value calculated in accordance with the particle diameter (Dd ₈₄ ) at 84.13% under the integrated sieve / the particle diameter (Dd ₅₀ ) at 50% under the integrated sieve. As the geometric standard deviation value (Dd ₈₄ / Dd ₅₀ ) is closer to 1, it means that the particle size distribution of the behavior particle diameter in the ink-jet ink is excellent.

  The dispersion stability of the ink for ink-jet was evaluated by visually evaluating the degree of sedimentation of the colorant of the ink-jet ink after placing 25 ml of ink in a 50-ml colorimetric tube and allowing it to stand at 60 ° C. for one month. Was evaluated.

1: The non-colored part is 10 cm or more.
2: The non-colored part is 5 cm or more and less than 10 cm.
3: The non-colored part is 1 cm or more and less than 5 cm.
4: The non-colored part is less than 1 cm.
5: A non-colored part is not recognized.

  The rate of change in the number-of-dispersed dispersed particle size of the inkjet ink is determined by the dynamic light scattering method “Dense Particle Size Analyzer FPAR-1000” (manufactured by Otsuka Electronics Co., Ltd.) after the ink is allowed to stand at 60 ° C. for 1 month. The value obtained by dividing the amount of change in the number-converted dispersed particle diameter before and after standing by the value before standing was expressed as a percentage as the rate of change.

The hue and saturation of the ink-jet ink is the same as that of the printed image recorded on plain paper “KB” (manufactured by KOKUYO Co., Ltd.) “multi-light source spectrophotometer MSC-IS-2D” (manufactured by Suga Test Instruments Co., Ltd.). The color index L ^* value, a ^* value, b ^* value and C ^* value are shown in accordance with JIS Z 8729.

The ink-jet ink has a weather resistance that covers half of the recording paper recorded on plain paper “KB” (manufactured by KOKUYO Co., Ltd.) with a metal foil, and “I Super UV Tester SUV-W13” (manufactured by Iwasaki Electric Co., Ltd.). The hue (L ^* value, a between the portion irradiated with ultraviolet rays and the portion not irradiated with ultraviolet rays by covering with a metal foil after continuous irradiation with ultraviolet rays at an irradiation intensity of 100 mW / cm ² for 6 hours. ^* Value, b ^* value) were measured using “multi-light source spectrocolorimeter MSC-IS-2D” (manufactured by Suga Test Instruments Co., Ltd.) and covered with a metal foil, which was not irradiated with ultraviolet rays. The light resistance was shown by the ΔE ^* value calculated according to the above equation 3 based on the measured value.

  Ink-jet ink clogging resistance is determined by placing the ink in a cartridge of an inkjet printer “Deskjet 970Cxi” (made by HEWLETT PACKARD) and printing on plain paper “KB” (made by KOKUYO Corporation) at room temperature. The degree of turbulence, chipping or non-ejection was visually evaluated and evaluated in the following five stages.

1: There is print disorder, chipping or non-ejection from the 1st sheet.
2: Print disorder, chipping, or non-ejection from the fifth sheet.
3: Print disorder, chipping or non-ejection from the 10th sheet.
4: Print disorder, chipping or non-ejection from the 20th sheet.
5: Print disorder, chipping or non-ejection from the 25th sheet.

<Composite Particle 1: Production of Composite Particle Powder>
To 7.0 kg of silica 1 (average primary particle size: 16 nm, BET specific surface area value: 204.3 m ² / g, light resistance ΔE ^* : 5.36), methyl hydrogen polysiloxane (trade name: TSF484: GE Toshiba Silicone) 140 g) was added while operating the edge runner, and mixed and stirred for 30 minutes at a linear load of 588 N / cm. The stirring speed at this time was 22 rpm.

Next, organic pigment B (type: phthalocyanine pigment, average particle size: 80 nm, BET specific surface area value: 87.9 m ² / g, geometric standard deviation value: 2.15, L ^* value: 23.04, a ^* (Value: 5.99, b ^* value: −13.16, C ^* value: 14.46, light resistance ΔE ^* : 8.83, ζ potential: −2.9 mV) 7.0 kg, the edge runner was operated The mixture was added over 30 minutes, and further mixed and stirred at a line load of 392 N / cm for 120 minutes to attach the organic pigment B to the methylhydrogenpolysiloxane coating, whereby composite particles 1 were obtained. The stirring speed at this time was 22 rpm.

The obtained composite particles 1 have an average primary particle diameter of 20 nm, a BET specific surface area value of 89.1 m ² / g, a number-converted average particle diameter of 26 nm, a volume-converted average particle diameter of 94 nm, and a geometric standard deviation value of 1.26. Among the hues, the L ^* value was 26.95, the a ^* value was 5.74, the b ^* value was -12.66, the C ^* value was 13.90, and the degree of desorption of the organic pigment was 4. . The coloring power was 93%, the light resistance ΔE ^* was 2.15, and the ζ potential was −22.8 mV. The coating amount of methyl hydrogen polysiloxane was 0.53% by weight in terms of C. The adhering organic pigment B was 33.19% by weight in terms of C (corresponding to about 100 parts by weight with respect to 100 parts by weight of the silica particle powder).

  From the observation result of the electron micrograph of the obtained composite particle 1, since almost no particles of the added organic pigment B are observed, it is confirmed that almost all of the organic pigment B is attached to the methylhydrogenpolysiloxane coating. Admitted.

<Example 1-1: Production of coloring material for ink-jet ink>
In a 3 l beaker, 300 g of the composite particle powder obtained above and 2 l of a 0.65 mol / l sodium hydroxide aqueous solution (0.2 times the theoretical amount capable of dissolving the silica particles and the surface modifier as core particles). The pH was 13.1 and the mixture was stirred at 60 ° C. for 30 minutes. This was filtered, washed with water, and then dried to obtain a colorant for inkjet ink.

The resulting ink-jet ink colorant has a silica content of 1.04% by weight in terms of Si, an average primary particle diameter of 15 nm, and a BET specific surface area value of 82.4 m ² / g, the number-converted average particle diameter was 21 nm, the volume-converted average particle diameter was 75 nm, and the geometric standard deviation value was 1.31. Among the hues, the L ^* value is 25.39, the a ^* value is −5.90, the b ^* value is −12.95, the C ^* value is 14.23, the coloring power is 105%, and the light resistance ΔE ^* is 3.54, ζ potential was −13.6 mV.

<Example 2-1: Production of inkjet ink>
In a sand mill, 67.7 parts by weight of ion-exchanged water and 1.3 parts by weight of polyoxyethylene lauryl ether are mixed and then mixed with 5.0 parts by weight of coloring material, 10 parts by weight of diethylene glycol, and 10 parts by weight of glycerin. Parts, 5 parts by weight of triethylene glycol monobutyl ether, 0.8 parts by weight of triethanolamine and 0.2 parts by weight of an antifoaming agent (silicon-based antifoaming agent) were added and mixed and dispersed for 3 hours, and then 0.5 μm. Inkjet ink was obtained by filtering using a membrane filter.

The obtained inkjet ink has a number-converted dispersion average particle diameter of 18 nm, a volume-converted dispersion average particle diameter of 51 nm, a visual evaluation of 5 among the dispersion stability, and a rate of change of the number-converted dispersed particle diameter of 6. 0.8%, Hue L ^* value 27.68, a ^* value 5.42, b ^* value 13.04, C ^* value 14.12, specific extinction coefficient ε _w 2.28, weather resistance The ΔE ^* value was 1.73 and the clogging resistance was 5.

  In accordance with the composite particle 1 and Example 1-1, composite particle powder, a colorant for inkjet ink, and an inkjet ink were prepared. Various characteristics of the production conditions and the obtained composite particle powder, the colorant for the inkjet ink, and the inkjet ink are shown.

Silica 1 and 2:
As core particles, silica particle powders 1 and 2 having the characteristics shown in Table 1 were prepared.

Organic pigments B, R, Y, G:
An organic pigment having the characteristics shown in Table 2 was prepared as the organic pigment.

<Manufacture of composite particle powder>
Composite particles 2-4:
Type of core particles, type and addition amount of surface modifier, line load and time for edge runner treatment in coating process of surface modifier, type of organic pigment in addition process of organic pigment, addition amount, edge runner treatment A composite particle powder was obtained in the same manner as the composite particle 1 except that the line load and time were variously changed.

  The production conditions at this time are shown in Table 3, and various characteristics of the obtained composite particle powder are shown in Table 4.

<Manufacture of coloring material for inkjet ink>
Examples 1-2 to 1-7, Comparative Examples 1-1 to 1-3:
The inkjet ink was prepared in the same manner as in Example 1-1, except that the type of composite particles, the pH of the solution at the time of alkali dissolution, the theoretical amount of the alkali to be added, the treatment temperature and the treatment time were variously changed. A colorant was obtained. The concentration (g / 100 ml) of the composite particle powder is the weight (g) of the composite particle powder with respect to 100 ml of the solution. In Example 1-2, freeze-drying was performed as a drying step.

  The production conditions at this time are shown in Table 5, and the characteristics of the coloring material of the obtained ink-jet ink are shown in Table 6.

<Inkjet ink>
Examples 2-2 to 2-7, comparative examples 2-1 to 2-11:
An inkjet ink was obtained in the same manner as in Example 2-1, except that the type of the colorant for the inkjet ink was variously changed.

  Table 7 shows the manufacturing conditions at this time, and Tables 8 and 9 show the characteristics of the obtained ink-jet ink.

The colorant of the inkjet ink according to the present invention has a fine primary particle size, a uniform particle size, high coloring power, excellent dispersibility, and excellent weather resistance. It is suitable as a coloring material for inkjet ink.
Moreover, since the inkjet ink according to the present invention is excellent in dispersibility, dispersion stability, and weather resistance, it is suitable as an inkjet ink.

Claims (3)

An ink-jet ink coloring material comprising fine composite particles in which silica is encapsulated in an organic pigment. 2. The colorant for an inkjet ink according to claim 1, wherein the silica contained in the fine composite particles is 0.001 to 9% by weight in terms of Si with respect to the fine composite particle powder. An ink-jet ink comprising the ink-jet ink colorant according to claim 1.