JP2012201849A - Ink for inkjet recording, ink cartridge, recording apparatus, and image-formed product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a yellow ink for inkjet recording in which a tinge of green or red is eliminated or reduced.SOLUTION: The recording ink for inkjet includes at least a pigment, a dispersing agent, a resin emulsion and water, in which at least an isoindoline-based pigment is selected as the pigment and another pigment is used and mixed so that its saturation is 65 or more and 80 or less, wherein the other pigment is a magenta pigment when the selected isoindoline-based pigment is yellow with a tinge of green; and the other pigment is a cyan pigment when the selected isoindoline-based pigment is yellow with a tinge of red.

Description

  The present invention relates to an ink jet ink that can provide high image saturation, is excellent in ejection stability, and is also excellent in ink storage stability.

The inkjet recording method is easy to make full color because the process is simpler than other recording methods, and there is an advantage that a high-resolution image can be obtained even with an apparatus having a simple configuration.
As ink-jet inks, dye-based inks in which various water-soluble dyes are dissolved in water or a mixture of water and an organic solvent are used. Dye-based inks have excellent color tone, but are resistant to light. There was a disadvantage that was inferior in nature. On the other hand, pigment-based inks in which carbon black and various organic pigments are dispersed are actively studied because they are superior in light resistance compared to dye-based inks. However, pigment-based inks tend to clog nozzles more easily than dye-based inks.

  Pigment dispersion is an operation in which a pigment existing as an aggregate is ground or pulverized to primary particles or a state close to primary particles. A general dispersion method of a pigment is a method in which a pigment and a dispersant are dispersed in a dispersion medium. The mixed pigment dispersion is ground or dispersed by combining a dispersing device such as a ball mill or a sand mill with a dispersion medium. As a dispersion medium, beads made of a material such as glass, iron, ceramics and the like with a diameter of several mm to 1 mm are used. By reducing the bead diameter, the number of beads per unit volume increases geometrically, the number of collisions between the pigment and the beads increases dramatically, and the fine particles of the pigment can be dispersed.

  Recently, with the demands for high contrast of liquid crystal displays, miniaturization of image pickup devices, high coloring and high definition of inkjet inks, there are increasing demands for finer particles and higher concentrations of pigments in dispersion compositions. However, the finer the particle diameter and the higher the pigment concentration, the easier it is to cause aggregation, making it difficult to obtain a stable dispersion composition.

In order to solve these problems, the improvement of the pigment itself (pigment surface treatment), the development of a dispersant having a good adsorptivity to the pigment, the development of a surfactant, and the proposal of a pigment dispersant have been proposed so far. Has been done.
Examples of pigments used in color filters and inkjet inks include phthalocyanine pigments, diketopyrrolopyrrole pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, isoindoline pigments, isoindolinone pigments, and azo pigments. Examples include pigments and dye lake pigments, and a number of pigment dispersants have been reported, particularly phthalocyanine pigments, anthraquinone pigments, and quinacridone pigments.

For example, a method of mixing a sulfonated pigment or a metal salt thereof with a pigment (for example, see Patent Documents 1 to 3), a method of mixing a substituted aminomethyl derivative (for example, see Patent Document 4), or a phthalimidomethyl derivative. A method (see, for example, Patent Document 5) is known. However, these methods are effective for pigments having a specific skeleton, but are not useful for pigments having a skeleton in which it is difficult to introduce a sulfone group, an aminomethyl group, a phthalimidomethyl group, or the like.
In particular, C.I. currently widely used in the field of color filters and inkjets. I. For isoindoline pigments represented by Pigment Yellow 139, it is difficult to introduce such a functional group, and only a pigment dispersant having a very limited structure has been reported so far.

  Patent Documents 6 and 7 propose a structure having an isoindoline skeleton and an acidic group introduced, but it is difficult to produce with high purity and a simpler and more highly stable pigment dispersing agent is proposed. It was sought after.

  On the other hand, many isoindoline-based pigments, which are yellow pigments, have a reddish or greenish color, and there are problems in using them as they are for yellow inks for full-color recording, and countermeasures are required.

  An object of the present invention has been made in view of the circumstances as described above, and is a yellow ink excellent in sharpness (saturation) useful for inkjet recording by using an isoindoline-based pigment that has been conventionally used as it is. Is to provide. Another object of the present invention is to provide an inkjet yellow ink to which a conventionally used pigment dispersant can be applied. Another object of the present invention is to provide an inkjet yellow ink having high saturation and excellent ejection stability and liquid stability. Still another object of the present invention is to provide an ink jet recording apparatus and a recording method using the yellow ink, and an image formed product.

  As a result of intensive studies, the inventors of the present invention selected an isoindoline pigment as a pigment in an inkjet recording ink (yellow ink) containing at least a pigment, a dispersant, a resin emulsion, and water, and have a chroma of 65 to 80. When the selected isoindoline pigment is a greenish yellow color, a magenta pigment is mixed to eliminate or soften the green color, and the selected isoindoline pigment is a reddish yellow color as follows. In this case, it was confirmed that a desired yellow ink was obtained by mixing a cyan pigment to eliminate or soften the reddishness. The present invention has been made based on these findings. That is, the said subject is achieved by the invention described below.

(1) It contains at least a pigment, a dispersant, a resin emulsion, and water, and at least an isoindoline pigment is selected as the pigment, and other pigments are used and mixed so that the saturation is 65 or more and 80 or less. An ink jet recording ink (yellow ink).

(2) The isoindoline pigment is C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment yellow 139, C.I. I. The inkjet recording ink according to (1), which is any one of CI Pigment Yellow 185.

(3) The inkjet recording ink according to (1) or (2), wherein the other pigment is any one of Pigment Red 122, Pigment Violet 19, and Pigment Blue 15: 3.

(4) The inkjet recording ink according to any one of (1) to (3), wherein the dispersant is a compound represented by the following general formula (1).

(In the formula, R represents an alkyl group having 1 to 20 carbon atoms, an allyl group or an aralkyl group, m represents an integer of 0 to 7, and n represents an integer of 20 to 200.)

(5) The inkjet recording ink according to (4), wherein the dispersant is POE (n = 40) β-naphthyl ether.

(6) The ink jet recording ink according to any one of (1) to (5), wherein the resin emulsion is an anionic self-emulsifying ether polyurethane resin emulsion.

(7) An ink cartridge containing the inkjet recording ink according to any one of (1) to (6).

(8) An ink jet recording apparatus comprising a head of a system for performing recording by discharging the ink jet recording ink according to any one of (1) to (6).

(9) An image forming method comprising printing on an image support using the ink jet recording apparatus according to (8).

(10) An image formed article printed on an image support by the image forming method described in (9) above.

(11) The image formed article as described in (10) above, wherein the image support is paper.

  According to the present invention, it is possible to provide an inkjet recording ink (yellow ink) having high image saturation and excellent ejection stability and liquid stability, an inkjet recording apparatus, an image recording method, and an image formed product. it can.

1 is a perspective view illustrating a configuration example of an ink jet recording apparatus of the present invention.

  The present invention relates to an inkjet recording ink (yellow ink) containing at least a pigment, a dispersant, a resin emulsion, and water, wherein at least an isoindoline pigment (yellow pigment) is selected as the pigment, and the saturation is 65. Other pigments are used and mixed so as to be 80 or less.

[Dispersant]
In the present invention, any pigment dispersant may be used, but by using a compound represented by the following general formula (1), the average particle size is small, and the standard deviation in the particle size distribution is also small. A small ink-jet recording ink can be obtained.

  In the formula, R represents an alkyl group having 1 to 20 carbon atoms, an allyl group or an aralkyl group, m represents an integer of 0 to 7, and n represents an integer of 20 to 200.

  In the general formula (1), n is preferably 20 or more and 200 or less, more preferably 30 or more and 50 or less. When n is less than 20, the dispersion stability tends to decrease, and the ink contains pigment having a large average particle size and a large standard deviation in the particle size distribution, so that satisfactory saturation cannot be obtained. On the other hand, when n is larger than 200, the viscosity of the ink increases, and printing by the ink jet method tends to be difficult. In the general formula (1), polyethyleneoxyethylene (POE) (n = 40) β naphthyl ether is more preferable.

  As the dispersant of the present invention, other than the compound represented by the general formula (1), a water-soluble styrene acrylic resin (HPD-96, manufactured by Johnson Polymer Co., Ltd.) or styrene represented by the following structural formula (2) Phenol-based phenols (Neugen EA-177, n = 25: estimated from HLB), etc.

  In the yellow ink of the present invention, the content of the dispersant is in the range of 10 to 200 parts by weight, preferably 15 to 100 parts by weight, and more preferably 20 to 50 parts by weight with respect to 100 parts by weight of the pigment. If it is the range of 10-200 mass parts, while the dispersibility of a pigment will improve, the storage stability with time of a pigment dispersion or an ink will improve.

[Resin emulsion]
In the ink of the present invention, a resin emulsion is added mainly for the purpose of improving image rubbing resistance and improving storage stability when a pigment is used as a colorant.
As resin of the resin emulsion, at least one selected from urethane resin and styrene-acrylic resin is used. As a result, a resin emulsion is formed as a protective colloid around the pigment particles, and ink storage stability, image quality, and image durability are improved as compared with the conventional case. Compared with other resins, these resins have a strong effect of forming a film on paper and improving the abrasion resistance of the printed matter, and thicken or aggregate when the ink lands on a recording medium such as paper. Because of its properties, it has the effect of suppressing the penetration of colored components and promoting the fixing to paper.
In particular, a urethane resin is preferable because it improves the dispersion stability of carbon black. When two or more kinds of resins are used in combination, if the combination is appropriate, the image quality and image durability can be further improved while ensuring the storage stability of the ink.

The urethane resin refers to a polymer compound mainly composed of a polyurethane skeleton whose main chain is a continuous urethane bond. A water dispersible urethane resin is particularly preferable. Examples of such water-dispersible urethane resins include polyurethane water obtained by introducing a hydrophilic component necessary for stable dispersion in water into the main chain of the polyurethane skeleton, or by dispersing with an external emulsifier. A dispersion is common, but a self-dispersion type (self-emulsification type) in which a hydrophilic component is introduced into the main chain is more preferable. Any of a colloidal dispersion, an emulsion, a suspension, and a slurry may be used.
As an example of a water-dispersible urethane resin, a diisocyanate compound is reacted with a diol compound such as a polyether diol, a polyester diol, or a polycarbonate diol and an acid group-containing diol such as a carboxylic acid group or a sulfonic acid group. Examples of the water-dispersible urethane resins (ester urethane resins, ether urethane resins, carbonate urethane resins, etc.) obtained from the above are preferable, and among these, anionic self-emulsifying ether urethane resins are particularly preferable.

  Examples of the diisocyanate compound include aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, and 4,4 ′. -Cycloaliphatic diisocyanate compounds such as dicyclohexylmethane diisocyanate, aromatic aliphatic diisocyanate compounds such as xylylene diisocyanate and tetramethylxylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, modified products of these diisocyanates (carbodiimide, Uretdione, uretoimine-containing metamorphs, etc.).

Examples of the diol compound include polyether diols such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyethylene adipate, polybutylene adipate, polyneopentyl adipate, and poly-3-methylpentyl. Examples thereof include polyester diols such as adipate, polyethylene / butylene adipate, polyneopentyl / hexyl adipate, polylactone diols such as polycaprolactone diol, and polycarbonate diol. From the viewpoint of ink storage stability, polyether-based, polyester-based, and polycarbonate-based diol compounds are preferable, polyether-based or polycarbonate-based are more preferable, and polyether-based are most preferable. Polyethers and polycarbonates are less susceptible to alteration due to hydrolysis in water, so that the storage stability is improved.
Examples of the acid group-containing diol include dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, and dimethylolbutyric acid. Particularly preferred is dimethylolbutanoic acid.

The urethane resin is synthesized by synthesizing an isocyanate-terminated prepolymer in a low-boiling solvent that does not react with isocyanate groups (acetone, etc.), introducing hydrophilic groups with diamines, polyols, etc., and then diluting with water for phase conversion. , Solvent method by distilling off the solvent to obtain polyurethane dispersion, prepolymer method in which isocyanate group-terminated prepolymer with hydrophilic group introduced is first synthesized, dispersed in water and then chain extended with amine, etc. Method, a method of using urethane prepolymer as a chain extender in an aqueous emulsifier solution, a step of sulfonating an aromatic ring of a urethane prepolymer having a free isocyanate group obtained from a hydrophobic polyol and an aromatic polyisocyanate Various methods, such as the process of using blocked isocyanate And it has, but not particularly limited.
When synthesizing by the prepolymer method, a low molecular weight polyhydroxy compound may be used. Examples of the low molecular weight polyhydroxy compound include the glycol and alkylene oxide low molar adducts mentioned as the raw materials for the polyester diol, trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane, and the alkylene oxide low molar adducts thereof. Can be mentioned.

In the case of a water-dispersible urethane resin, a method is generally known in which a urethane prepolymer prepared in an organic solvent phase is phase-inverted and emulsified and further chain-extended in an aqueous phase. In this case, polyamines such as diamine are generally used as chain extenders. Specifically, the urethane prepolymer is subjected to water extension or di- or triamine extension after neutralizing an acid group derived from dimethylolalkanoic acid or while neutralizing. As the polyamine used as a chain extender for amine extension, diamine or triamine is usually used. Specific examples thereof include hexamethylene diamine, isophorone diamine, hydrazine, and piperazine.
However, it has been found that when a urethane resin using polyamines is used as a chain extender, the storage stability of the ink tends to be poor. This is because an amine-extended urethane resin (urethane resin containing a polyurethane urea moiety) is prone to hydrolysis, and polyamines produced by hydrolysis also act as a flocculant in the pigment dispersion. It is presumed to have a bad influence on.

The urethane resin can be used in the form of an alkali metal salt such as Li, Na, or K, an organic amine salt such as ammonia, dimethylamine, or (mono, di, tri) ethanolamine. These can be obtained by further neutralizing the urethane resin obtained by the aforementioned method.
The base used for this neutralization can be appropriately selected according to the counter ion of the desired salt, for example, alkylamines such as butylamine and triethylamine, monoethanolamine, diethanolamine, triethanolamine and the like. Inorganic bases such as alkanolamine, morpholine, ammonia, sodium hydroxide and the like can be mentioned.

Next, the styrene-acrylic resin will be further described.
This resin can be prepared in an aqueous medium by the well-known free radical emulsion polymerization method, and a homopolymer produced from one type of monomer or a copolymer produced from more than one type of monomer can be used. Polymers containing monomers that form water-insoluble homopolymers are preferred as well as copolymers of such monomers. It can also include monomers that form water-soluble homopolymers if the entire polymer composition is sufficiently water-insoluble to form a latex.
These polymers can be produced by emulsion polymerization, solution polymerization, suspension polymerization, dispersion polymerization, ionic polymerization (cation, anion), atomic transfer radical polymerization, and other polymerization methods well known in the polymerization art.

An example of a preferred polymer is a styrene-acrylic resin prepared by free radical polymerization of vinyl monomers in an aqueous emulsion. The polymer latex is preferably a homopolymer or copolymer or cross-linked polymer containing an ethylenically unsaturated hydrophobic monomer that produces a water-insoluble homopolymer, provided that the entire polymer composition is water-insoluble enough to form a latex. Also preferred are copolymers of monomers that also contain ethylenically unsaturated hydrophilic monomers that form water-soluble homopolymers.
These styrene-acrylic resins can be produced by emulsion polymerization, dispersion polymerization, suspension polymerization, grinding or solution / bulk polymerization. Detailed information on this method and stabilizer is described in “Emulsion Polymerization and Emulsion Polymer” (PA Lovell, MS El-Asser, John Wiley & Sons Ltd., England, 1977) and the like. ing.

  Commercially available resin emulsions include J-450, J-734, J-7600, J-352, J-390, J-7100, J-741, J-74J, J-511, J-840, J-775. , HRC-1645, HPD-71, PDX-6102B, JDX-5050 (styrene-acrylic resin emulsion, manufactured by BASF), UC-3900 (styrene-acrylic resin emulsion, manufactured by Toagosei Co., Ltd.), SF460, SF460S, SF420, SF110, SF300, SF361 (polyurethane resin emulsion, manufactured by Nihon Unicar), W-6020, W-5025, W-5661, W-6010 (polyurethane resin emulsion, manufactured by Mitsui Chemicals, Inc.), and the like.

  The addition amount of the resin emulsion is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the whole ink. If the amount is less than 0.1% by mass, sufficient fixability may not be obtained. If the amount exceeds 10% by mass, the composition has a large solid content and a small amount of solvent. Drying and solidification are likely to occur, and dischargeability may be reduced.

〔water〕
As the water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used.
In addition, the use of water sterilized by irradiation with ultraviolet rays or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be prevented when the ink is stored for a long period of time.

[Pigment]
The pigment mainly used in the present invention is an isoindoline pigment (yellow pigment).
The isoindoline pigment is a pigment obtained by condensing 1,3-diiminoisoindoline and an active methylene compound. I. Pigment yellow 139. In addition, in the present invention, C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment Yellow 185 or the like is preferably used.

  C. I. Pigment Yellow 109 is an organic compound having the following structural formula (3) and a greenish yellow pigment.

  C. I. Pigment Yellow 110 is an organic compound having the following structural formula (4) and a reddish yellow pigment.

  C. I. Pigment Yellow 139 is an organic compound having the following structural formula (5) and is a reddish yellow pigment.

  C. I. Pigment Yellow 185 is an organic compound having the following structural formula (6) and a greenish yellow pigment.

  There is no restriction | limiting in particular as an average particle diameter of the said isoindoline-type pigment, Although it can select suitably according to the objective, Since it is excellent in coloring property, so that it is fine, it is 10-200 nm, Preferably it is 10-150 nm. The particle size of the isoindoline pigment can be adjusted by selecting the isoindoline pigment, the dispersant and the dispersion medium, setting the dispersion conditions, the filtration conditions, and controlling the particle size of the isoindoline pigment. Thus, clogging of the head nozzle can be suppressed, and the storage stability of the ink composition, the transparency of the ink composition, and the curing sensitivity can be maintained.

  Preferred examples of pigments other than the yellow pigment (hereinafter also referred to as “complementary color pigments”) mixed so that the saturation of the yellow ink of the present invention is 65 or more and 80 or less are C.I. I. Pigment red 122, C.I. I. Pigment violet 19, C.I. I. Pigment blue 15: 3.

  C. I. Pigment Red 122 is an organic compound having the following structural formula (7) and is a magenta pigment.

  C. I. Pigment Violet 19 is an organic compound having the following structural formula (8) and is a magenta pigment.

  C. I. Pigment Blue 15: 3 is an organic compound having the following structural formula (9) and is a cyan pigment.

  The average particle diameter of the complementary color pigment is not particularly limited as in the case of the average particle diameter of the isoindoline pigment, and can be appropriately selected according to the purpose. It is -200 nm, Preferably it is 10-150 nm. As in the case of the isoindoline pigment, the particle diameter of the complementary color pigment can also be adjusted by selecting the complementary color pigment, the dispersant and the dispersion medium, setting the dispersion conditions, and the filtration conditions.

  The isoindoline pigment and the complementary color pigment are mixed in such a ratio that the saturation of the resulting yellow ink is in the range of 65 to 80. : 1 to 99.9: 0.1, preferably 99.2: 0.8 to 99.6: 0.4.

<Saturation>
The ink-jet ink (yellow ink) of the present invention has a saturation in the range of 65 to 80. If it is less than 65, the color reproducibility may be poor, and if it exceeds 80, it becomes a red or greenish yellow. .
According to the use of yellow ink having a saturation of 65 to 80, the recorded (printed) image has a good sharpness.
The saturation (L *) referred to in the present invention is determined by the following measurement / test.

1. Definition of measurement items The measurement items defined by this test method and their meanings are defined below.
L *: Brightness of liquid calculated from the measurement spectrum of UV spectrophotometer (Hitachi, U-3300) a *: Calculated from measurement spectrum of UV spectrophotometer (Hitachi, U-3300) Liquid color difference a *
b *: Liquid color difference b * calculated from the measured spectrum of a UV spectrophotometer (Hitachi, U-3300)

2. Equipment configuration (1) UV spectrophotometer (manufactured by Hitachi, U-3300)
(2) Precision electronic balance (3) Quartz cell (optical path length: 10mm)
(4) Pure water (for blank measurement, dilution, washing)

3. Test environment 25 ℃

4). Measurement procedure <No. 1> Preparation of measurement sample About 0.5 g of the sample is precisely weighed with a precision electronic balance, diluted with pure water to about 20 g, and stirred uniformly. About 0.5 g of this diluted sample is precisely weighed with a precision electronic balance, pure water is added to dilute to about 50 g, and the mixture is stirred uniformly to prepare a measurement sample.
<No. 2> Measurement condition setting (photometer condition, measurement condition)
Data mode: Abs
Scan speed: 300 nm / min
Wavelength range: 800-200 nm
Photometric value range: 3.000 to 0.000 Abs
Slit: 2.0nm
Photomultiplier voltage: Automatic control Light source switching wavelength: Automatic switching (340nm)
Baseline correction mode: User 1
Sampling interval: 0.5 nm
High resolution measurement: off
Initial waiting time: 0 sec
<No. 3> Procedure (i) Measure and set the baseline. (Ii) Put the measurement sample solution into the cell and set it on the sample side. (Iii) The spectral spectrum of the sample is measured. (Iv) L *, a *, b * are obtained from the measured spectrum.
Saturation (L *) is calculated using the above a and b values.

I mean.

[Other ingredients]
In addition to the pigment, dispersant, resin emulsion, and water, the yellow ink of the present invention contains a water-soluble organic solvent, a wetting agent, a penetrating agent, a pH adjusting agent, a preservative, and the like as necessary. May be.

Specific examples of the water-soluble organic medium include alcohols such as methanol, ethanol, 1-propanol and 2-propanol, polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and glycerin, N-methylpyrrolidone, 2 -Pyrrolidone derivatives such as pyrrolidone, ketones such as acetone and methyl ethyl ketone, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and nonionic, anionic, cationic and amphoteric surfactants.
The content of the water-soluble organic medium in the ink is preferably 1 to 50% by mass.

The wetting agent is added for the purpose of preventing clogging of the nozzles of the recording head due to drying. Specific examples of the wetting agent include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, 1,3-butanediol, 1,3-propanediol, and 2-methyl-1,3-propane. Diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, 1,2 Polyhydric alcohols such as 1,4-butanetriol, 1,2,3-butanetriol, and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene Polyhydric alcohol alkyl ethers such as glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, nitrogen-containing heterocyclic compounds such as ε-caprolactam, formamide, N-methylformamide, N, Amides such as N-dimethylformamide, alcohols such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine and triethylamine And amines, sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, thiodiethanol, propylene carbonate, ethylene carbonate, and γ-butyrolactone. These are used alone or in combination with water.
The content of the wetting agent in the ink is preferably 1 to 50% by mass.

The penetrant is added for the purpose of improving the wettability between the ink composition and the recording material and adjusting the penetration speed. Specific examples of the penetrant include 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, and 2-methyl-2-propyl-1,3-propanediol. 3,3-dimethyl-1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-dimethyl-2,4-pentanediol, 2-ethyl-1,3- Aliphatic diols such as hexanediol, 2,5-dimethyl-2,5-hexanediol, and 5-hexene-1,2-diol are listed. Among these, 2,2,4-trimethyl-1,3-pentanediol and 2-ethyl-1,3-hexanediol are particularly preferable.
The content of the penetrant in the ink is preferably 1 to 30% by mass.

[Preparation of inkjet ink]
The ink of the present invention can be prepared by a known method. For example, pigment dispersion, water, water-soluble organic solvent, etc. are stirred and mixed using a sand mill, ball mill, roll mill, bead mill, nanomizer, homogenizer, ultrasonic disperser, etc., and coarse particles are filtered through a filter, a centrifugal separator, etc. And obtained by deaeration as necessary.

[Ink cartridges, inkjet recording devices, etc.]
The pigment-based ink-jet ink of the present invention is suitable for an ink set for ink-jet recording that forms an image on an image support by overlaying a plurality of inks of different hues to form a color image, for example, and an ink cartridge that accommodates this Can be used. The pigment-based ink-jet ink of the present invention can be image-formed by an ink-jet printing apparatus that forms an image by discharging (recording) the image on an image support such as paper. Examples of the printing method include a continuous jet type and an on-demand type. Examples of the on-demand type include a piezo method, a thermal ink jet method, and an electrostatic method.

In the present invention, the ink receptor (image support) is preferably used regardless of whether it has an absorptivity for ink such as paper or a substantially non-absorptivity for the ink composition. Specific examples of the receiver to which the ink jet recording method according to the present invention can be applied include plastic sheets based on polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polysulfone, ABS resin, polyvinyl chloride, brass, iron, aluminum, SUS, a metal surface such as copper or a non-metallic base material, a recording medium that has been subjected to a metal coating process by vapor deposition or the like, a recording medium that has been subjected to water-repellent treatment using paper as a base material, and an inorganic material are baked at a high temperature And a recording medium made of a so-called ceramic material.
Of these, paper is most preferable from the viewpoint of economy and the naturalness of images.

An ink cartridge (hereinafter referred to as a cartridge) and an ink jet recording apparatus of the present invention will be described with reference to FIG.
In FIG. 1, an ink cartridge 20 in which the ink jet ink of the present invention is accommodated is accommodated in a carriage 18. Here, a plurality of cartridges 20 are provided for convenience, but it is not necessary to have a plurality. In such a state, the ink for inkjet is supplied from the cartridge 20 to the droplet discharge head 18 a mounted on the carriage 18. In FIG. 1, the discharge nozzle surface is in an invisible state because it faces downward, but ink jet ink is discharged from the discharge nozzle.
The droplet discharge head 18 a mounted on the carriage 18 moves while being guided by guide shafts 21 and 22 by a timing belt 23 driven by a main scanning motor 24. On the other hand, a specific coated paper (image support) is placed at a position facing the droplet discharge head 18 a by the platen 19. In the drawings, reference numeral 1 denotes an ink jet recording apparatus, 2 denotes a main body housing, 16 denotes a gear mechanism, 17 denotes a sub-scanning motor, 25 and 27 denote gear mechanisms, and 26 denotes a main scanning motor.
When a pattern is formed on the image support using the ink jet recording apparatus containing the ink jet ink according to the present invention, an image forming body printed on the image support on demand is obtained. Further, replenishment of ink for ink jet can be replaced in units of ink cartridges.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to a present Example. In addition, the number of parts here represents a mass part. Y pigment means yellow pigment.

  Table 1 shows Y pigments (yellow pigments) α, β, γ, and δ used in the examples and Y pigments (yellow pigments) ε used in the comparative examples. Pigment species ε (Pigment Yellow 74) is an azo pigment.

  Table 2 shows complementary color pigments ζ, ρ, and η used in the examples.

また、実施例及び比較例で用いる分散剤Ｉ〜ＶＩＩを表３、樹脂エマルジョンａ、ｂ及びｃを表４に示す。

Table 3 shows dispersants I to VII used in Examples and Comparative Examples, and Table 4 shows resin emulsions a, b, and c.

  The above-mentioned Y pigment, complementary color pigment and dispersant are dispersed or dissolved in distilled water to give a total amount of 1000 parts. 1-No. 15 was prepared.

After premixing the mixture (dispersion) in Table 5 above, 0.03 mm zirconia beads (density: 6.03 × 10 ⁻⁶ g / m ² ) using a bead mill disperser (manufactured by Kotobuki Industries Co., Ltd., UAM-015). Was dispersed for 15 minutes at a peripheral speed of 8 m / s and a liquid temperature of 30 ° C., and then the coarse particles were centrifuged with a centrifuge (Model 3600, manufactured by Kubota Corporation) to obtain an average particle size of 100 nm of the dispersion. .

[Examples 1 to 13, Comparative Examples 1 to 5]
The ink components were mixed so that the total amount was 100 parts.
Basic ink formulation Pigment solid content 8.0 parts Glycerin 20.0 parts Diethylene glycol 10.0 parts 2-ethyl-1,3-hexanediol 3.0 parts 2-pyrrolidone 3.0 parts Resin emulsion 2.0 parts Distilled water The remaining ink was prepared, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum degassed to obtain ink jet recording inks (yellow inks) of Examples and Comparative Examples shown in Table 6.

  The ink-jet recording ink was filled into an ink pack for an ink-jet printer (IPSiO GX 5000) manufactured by Ricoh Co. to prepare an ink cartridge.

  The resulting yellow ink was evaluated for solid density, saturation, ejection stability, and ink storage stability. The evaluation results are summarized in Table 7.

<Evaluation of solid density>
Printing was performed on a PPC paper XEROX 4200 manufactured by Xerox Co., Ltd., and the printed image was measured with an Xrite densitometer. A blue filter was not used, 10 PPC paper Type 6200 made by Ricoh Co., Ltd. were bundled and measured as a base, and evaluated according to the following criteria. At this time, the dry coating condition is 435 mg / A4.
○: 0.90 or more Δ: Less than 0.90 0.70 or more ×: Less than 0.70

<Saturation evaluation>
Yellow ink was measured with a UV spectrophotometer (U-3300) manufactured by Hitachi in accordance with the measurement method described above, and evaluated according to the following evaluation criteria.
×: Greater than saturation 80 ○: More than 65 and less than 80 ×: Less than 65

<Discharge stability evaluation>
Put the printer in a constant temperature and humidity chamber, set the environment in the bath to a temperature of 32 ° C. and a humidity of 30% RH. After printing the following print pattern charts continuously for 20 sheets, put the printer into a pause state for 20 minutes. It was repeated 50 times, and after a total of 1,000 copies were printed, the nozzle plate was observed with a microscope to determine the presence or absence of sticking.
-Print pattern chart-
In the printing pattern, each ink was printed at a duty of 100% in a chart in which the printing area in the image area is 5% of the printing area of each color in the entire area of the paper. The printing conditions were a recording density of 300 dpi and one-pass printing.
○: No sticking near the nozzle △: Some sticking near the nozzle ×: Sticking near the nozzle

<Evaluation of ink storage stability>
Each ink was put in a polyethylene container, sealed, stored at 70 ° C. for 3 weeks, and then the particle size, surface tension, and viscosity were measured and evaluated according to the rate of change from the initial physical properties as follows.
○: Within 10% △: Within 30% Over 10% ×: Over 30%

  As shown in Table 7, according to the present invention, it is possible to obtain an ink jet recording ink (yellow ink) having a high solid density and saturation, and excellent discharge stability and liquid stability.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Main body housing | casing 16 Gear mechanism 17 Subscanning motor 18 Carriage 18a Droplet discharge head 19 Platen 20 Ink cartridge (cartridge)
21 Guide shaft 22 Guide shaft 23 Timing belt 24 Main scanning motor 25 Gear mechanism 26 Main scanning motor 27 Gear mechanism

Japanese Patent Publication No.41-2466 JP 63-172772 A Japanese Patent Publication No. 50-4019 Japanese Examined Patent Publication No. 39-16787 JP-A-55-108466 Japanese Patent Laid-Open No. 2005-179489 JP 2007-120777 A

Claims (11)

  It contains at least a pigment, a dispersant, a resin emulsion, and water, and at least an isoindoline pigment is selected as the pigment, and other pigments are used and mixed so that the saturation is 65 or more and 80 or less. An ink jet recording ink.   The isoindoline pigment is C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment yellow 139, C.I. I. The inkjet recording ink according to claim 1, which is any one of CI Pigment Yellow 185.   The inkjet recording ink according to claim 1 or 2, wherein the other pigment is any one of pigment red 122, pigment violet 19, and pigment blue 15: 3. The inkjet recording ink according to claim 1, wherein the dispersant is a compound represented by the following general formula (1).

(In the formula, R represents an alkyl group having 1 to 20 carbon atoms, an allyl group or an aralkyl group, m represents an integer of 0 to 7, and n represents an integer of 20 to 200.)   The inkjet recording ink according to claim 4, wherein the dispersant is POE (n = 40) β-naphthyl ether.   6. The ink jet recording ink according to claim 1, wherein the resin emulsion is an anionic self-emulsifying ether polyurethane resin emulsion.   An ink cartridge containing the inkjet recording ink according to claim 1.   An ink jet recording apparatus comprising: a head for recording by discharging the ink jet recording ink according to claim 1.   An image forming method comprising printing on an image support using the ink jet recording apparatus according to claim 8.   An image formed article printed on an image support by the image forming method according to claim 9.   The image-formed product according to claim 10, wherein the image support is paper.

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