JP2003171589A - Pigment ink for ink-jet, and ink-jet cartridge, ink-jet image recording method and ink-jet recorded image using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pigment ink for ink-jet which gives an ink-jet recorded image excellent in gloss properties and transparency and improved in light resistance and fretting resistance, and to provide an ink-jet cartridge, an ink-jet image recording method and an ink-jet recorded image using the same. <P>SOLUTION: The pigment ink for ink-jet comprises a pigment particle, a hydrophilic solvent, water and a latex, where the absolute value of the average zeta potential of the latex is smaller than the absolute value of the average zeta potential of the pigment particle. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an inkjet pigment ink, an inkjet cartridge using the same, an inkjet image recording method, and an inkjet recorded image.

[0002]

2. Description of the Related Art Ink jet recording is a technique for ejecting minute droplets of ink by various operating principles and adhering them to a recording medium to record images, characters, etc. It has an advantage that it can be easily colored.

In addition, due to recent technological advances, ink jet printing using dye ink is accelerating its widespread use with the high image quality approaching that of silver halide photography and the cost reduction of the apparatus.

The dye is soluble in a solvent, and the dye molecule is colored in a molecular state or a cluster state. Therefore,
Since the environment of each molecule is similar, its absorption spectrum is sharp, and it exhibits high purity and vivid color. Furthermore, since there is no granular pattern due to particles and scattered light or reflected light does not occur, it is possible to obtain an inkjet image having high transparency and a clear hue.

On the other hand, however, when the molecules are destroyed by a photochemical reaction or the like, the decrease in the number of molecules is reflected in the coloring density as it is, so that the light resistance is poor. Although an ink jet recorded image using a dye ink has a high image quality, the image quality is largely deteriorated due to storage over time, and a technique that surpasses silver salt photography from the viewpoint of image storability has not yet appeared.

In contrast to dye inks, pigment inks using pigments having good light resistance as colorants are used as inks for applications requiring an image resistant to fading by light. However, since the pigment is present as pigment particles as compared with a dye, it is more susceptible to light scattering, and the abrasion resistance is reduced due to aggregation of pigment particles on the printed surface,
Alternatively, since it gives an image having low glossiness and no transparency, it has a drawback that it is inferior to dyes in terms of physical properties of printed images and color reproducibility.

In order to overcome this drawback, it has been attempted to improve the color reproduction by preparing a pigment ink having a small dispersed particle diameter as a pigment particle by dispersion. However, in general, the smaller the primary particles, the more difficult it is to secure the dispersion and stability of the pigment, and the adverse effects such as an increase in the viscosity are caused, and the pigment has not been put into practical use.

Further, as a method of improving scratch resistance, it is known to add a water-insoluble polymer dispersion liquid, so-called latex, to a pigment ink. Although the scratchability is improved, there is a problem in that the glossiness and transparency of the obtained print image quality do not reach that of the silver salt image.

On the other hand, as a technique for making fine particles of a pigment, for example, a pigment that can be dispersed without a dispersant (hereinafter, this pigment is referred to as a self-dispersion pigment) or the surface of the pigment particle is made of a polymer compound having dispersibility. Coated polymer-coated pigments and the like are known.

The above-mentioned self-dispersing pigment is, for example, WO97 /
48769, JP-A-11-57458, JP-A-11-189739, JP-A-2000-26509.
4, a method for modifying the surface of pigment particles with a sulfonating agent, an oxidizing agent, etc., JP-A-11-49974, JP-A-2000-273383, 2000-3.
A method for adsorbing the pigment derivative described in JP-A-03014 on the surface of pigment particles by a treatment such as milling, Japanese Patent Application No. 2000-
377068, 2001-1495, 2001-2
A pigment ink having a small particle size and good dispersion stability can be obtained by dissolving the pigment and the pigment derivative described in 34966 in a solvent and then crystallization in a poor solvent. It can be prepared.

The polymer-coated pigment is prepared, for example, by dispersing the pigment particles described in JP-A-8-71405 with a polymer compound, dissolving the polymer compound in an organic solvent, and then phase inversion emulsifying in water. , Color Material Association, 70, 503 (19
97), a method of causing a monomer to be adsorbed on the surface of the pigment particle and then polymerizing it, Journal of Coloring Materials, 69, 743 (19).
96) and 72, 748 (1999), a method of introducing a polymerization initiator to the surface of the pigment particle and then polymerizing it with a monomer, etc., which forms a strong polymer film on the surface of the pigment particle. Since the free high molecular compound does not exist in the pigment ink, a pigment ink having high dispersion stability can be obtained.

However, although the pigment particles obtained by the method described above all have high dispersion stability, the ink jet formed image formed by the pigment particles is
Compared with silver salt images, they have problems in light resistance, scratch resistance, glossiness, etc., and further technical improvement is required.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to improve the light resistance, scratch resistance, glossiness and transparency of ink jet recorded images. Another object of the present invention is to provide an inkjet cartridge, an inkjet image recording method and an inkjet recorded image using the same.

[0014]

The above objects of the present invention have been achieved by the following constitutions.

1. In an inkjet pigment ink containing pigment particles, a hydrophilic solvent, water and a latex,
An ink-jet pigment ink, wherein the absolute value of the average zeta potential of the latex is smaller than the absolute value of the average zeta potential of the pigment particles.

2. 2. The inkjet pigment ink according to item 1, wherein the redispersion coefficient represented by the formula (1) is 3 or less.

3. The pigment ink for inkjet according to the item 1 or 2, wherein the secondary volume average particle diameter of the pigment particles is 10 to 90 nm.

4. Static surface tension is 25-45 mN / m
4. The inkjet pigment ink according to any one of items 1 to 3, wherein:

5. pH is 7.0 or more, The pigment ink for inkjets of any one of said 1-4 characterized by the above-mentioned.

6. Any of the above items 1 to 5, wherein the hydrophilic solvent content is 5 to 70% by mass.
Item 5. The inkjet pigment ink according to the item.

7. The inkjet pigment ink according to any one of items 1 to 6, wherein the polyvalent metal ion content is 5 ppm or less.

8. Item 8. The inkjet pigment ink according to any one of items 1 to 7, which contains an anionic surfactant.

9. Item 8. The inkjet pigment ink according to any one of items 1 to 7, which contains a nonionic surfactant.

10. Item 8. The inkjet pigment ink according to any one of items 1 to 7, which contains a cationic surfactant.

11. Item 8. The inkjet pigment ink according to any one of items 1 to 7, which contains an anionic surfactant and a nonionic surfactant.

12. 12. The inkjet pigment ink according to any one of items 1 to 11, which contains a water-soluble polymer.

13. Any one of the above items 1 to 12, wherein the pigment particles have a polar group on the surface.
Item 5. The inkjet pigment ink according to the item.

14. 13. The inkjet pigment ink according to any one of items 1 to 12, wherein the surface of the pigment particles is coated with a polymer compound.

15. An ink jet cartridge comprising an ink containing portion containing at least one pigment ink for ink jet according to any one of items 1 to 14.

16. 15. An inkjet image recording method, wherein an image is formed using at least one of the inkjet pigment inks according to any one of 1 to 14 above.

17. An inkjet recorded image formed by performing inkjet image recording using at least one pigment ink for inkjet according to any one of 1 to 14 above.

The inventors of the present invention have made extensive studies as to improvement of light resistance, scratch resistance, glossiness and transparency of an output image by using a pigment ink. As a result, the absolute value of the average zeta potential of the latex is It has been found that this can be realized by using a pigment ink characterized by being smaller than the absolute value of the average zeta potential of.

The pigment ink, as an ink jet image quality, has not yet reached that region as compared with the photographic image quality, and has a property inferior in light resistance, scratch resistance, glossiness or transparency.

As described above, the use of latex in the pigment ink is recognized to improve scratch resistance to some extent, but in terms of glossiness, light resistance, and transparency, the quality still reaches the range of silver salt images. It wasn't.

As a result of further investigations on the above problems, the inventors of the present invention generally have a small zeta potential difference between the pigment particles and the latex, so that the pigment particles and the latex are randomly aggregated on the surface of the recording medium. As a result, it was found that the surface of the obtained printed image was rough.

In the present invention, paying attention to the zeta potential difference between the pigment particles and the latex, and by using the latex having an average zeta potential smaller than the absolute value of the average zeta potential of the pigment particles, the glossiness, light resistance and It has been found that the transparency is remarkably improved.

Further, in order to solve the above-mentioned problems, by using a self-dispersion pigment which does not require a dispersant or a pigment particle whose surface is coated with a polymer resin, the particle size of the obtained pigment particle is small and the specific surface area is increased. As a result, it is possible to obtain a certain degree of glossiness and transparency.

Furthermore, the effect of the present invention is to set the redispersion coefficient of the pigment ink, the secondary particle diameter of the pigment particles, the pH of the pigment ink, the static surface tension, the polyvalent metal ion, and the amount of the ink solvent within a specific range. In addition, it was found that it can be further exerted by using a surfactant and a polymer compound.

The details of the present invention will be described below. In the invention according to claim 1, in an inkjet pigment ink containing pigment particles, a hydrophilic solvent, water and latex, the absolute value of the average zeta potential of the latex is smaller than the absolute value of the average zeta potential of the pigment particles. This is a characteristic, and the difference between the absolute value of the average zeta potential of the pigment particles and the absolute value of the average zeta potential of the latex is preferably 7 or more, more preferably 15 or more.

The absolute value of the average zeta potential of the pigment particles is preferably 50 mV or more, more preferably 60 mV or more, and particularly preferably 60 to 100.
mV.

The absolute value of the zeta potential of each latex is preferably in the range of 10 to 100 mV, more preferably 15 to 90 mV.

In the present invention, the average zeta potential of pigment particles or particles in latex is, for example, ELS-8.
00 (manufactured by Otsuka Electronics Co., Ltd.) or the like, but it is preferable to use a microscope electrophoresis method capable of measuring the zeta potential of individual latex particles, for example, ZEECOM ZC-manufactured by Microtec. 2000
This device can be used to measure the zeta potential of 500 or more pigment particles or latex particles and obtain the arithmetic mean value thereof.

Next, the latex that can be used in the present invention will be described. The latex that can be used in the present invention is not particularly limited, and examples thereof include styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylic ester copolymer, polyurethane, silicone-acrylic copolymer and Examples of the latex include acrylic modified fluororesin.
The latex may be one in which polymer particles are dispersed with an emulsifier, or one without an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer having a solubilizing group graft-bonded thereto or a monomer having a solubilizing group It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble portion.

In the pigment ink of the present invention, it is particularly preferable to use soap-free latex. Soap-free latex is a latex that does not use an emulsifier, and a polymer having a water-soluble group such as a sulfonic acid group and a carboxylic acid group (for example, a polymer having a solubilizing group graft-bonded thereto, a solubilizing group Polymer obtained from a monomer having an insoluble portion and a monomer having an insoluble portion) is used as an emulsifier.

In recent years, as latex polymer particles, in addition to a latex in which polymer particles having a uniform particle size are dispersed, a core having a different composition at the central portion and the outer edge portion
Although there is a latex in which shell-type polymer particles are dispersed, this type of latex can also be preferably used.

In the pigment ink of the present invention, the average particle size of the polymer particles in the large particle size and small particle size latex is 10 n.
m or more and 300 nm or less, 10 nm or more, 150
More preferably, it is not more than nm. If the average particle size of the latex exceeds 300 nm, the glossiness of the image deteriorates, and if it is less than 10 nm, the water resistance and scratch resistance become insufficient. The average particle size of the polymer particles in the latex is
It can be determined by a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, or a laser Doppler method.

In the pigment ink of the present invention, the latex is preferably added so that the solid content is 0.1% by mass or more and 20% by mass or less based on the total mass of the ink. It is particularly preferable that the amount added is 0.5% by mass or more and 10% by mass or less. If the solid content of the latex is less than 0.1% by mass, it is difficult to exert a sufficient effect on water resistance, and if it exceeds 20% by mass, the viscosity of the ink increases with time and the particle size of the pigment dispersion is increased. In many cases, problems occur in terms of ink storability, such as an increase in ink liquor.

As a method for controlling the particle size and zeta potential of each latex used in the present invention to desired values, for example, salt concentration, stirring strength, activator, etc. at the time of latex preparation are appropriately adjusted to obtain desired characteristics. Can be obtained.

As the pigment that can be used in the present invention,
Known colored organic or colored inorganic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthaloni pigments, etc. Examples include polycyclic pigments, dye lakes such as basic dye type lakes and acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black and daylight fluorescent pigments, and inorganic pigments such as carbon black. However, the present invention is not limited to these.

Specific organic pigments are exemplified below. Examples of magenta or red pigments include C.I. I.
Pigment Red 2, C.I. I. Pigment Red 3,
C. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I.
I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1,
C. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I.
I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 166, C.I. I.
Pigment Red 177, C.I. I. Pigment Red 1
78, C.I. I. Pigment Red 222 and the like.

Examples of pigments for orange or yellow include C.I. I. Pigment Orange 31, C.I.
I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I.
Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 9
3, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 13
8 etc. are mentioned.

As the pigment for green or cyan,
For example, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 1
5: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.

Examples of black pigments include C.I. I. Pigment Black 1, C.I. I. Pigment Black 6, C.I. I. Pigment Black 7 and the like.

In the present invention, the method of applying the zeta potential defined above to the pigment particles is not particularly limited, but, for example, the type and amount of the surfactant used at the time of dispersing the pigment, the addition of an additive having a charge are added. A desired zeta potential can be obtained by appropriately selecting the above.

The hydrophilic solvent that can be used in the present invention is not particularly limited, but it is preferable to use the compound represented by the following general formula (1). General formula (1) AB In formula, A represents a group containing a hydrophilic substituent, and B represents a hydrophobic group.

The group represented by A is a group containing a hydrophilic substituent, and as the hydrophilic substituent, a hydroxy group, a carboxyl group, a sulfoxide group, a sulfone group, a sulfonic acid group, and 2-keto-1. -Pyrrolidinyl group and the like.
Of these, a hydroxy group is preferable.

B represents a hydrophobic group, preferably an aliphatic or aromatic hydrocarbon group having 3 to 10 carbon atoms.
Further, B is preferably an aliphatic group having 4 to 8 carbon atoms.

The compound represented by the general formula (1) has a structure similar to that of a general surfactant. A general surfactant has a characteristic of forming micelles in an aqueous solution at a low concentration.

The compound represented by the general formula (1) preferably does not have such micelle forming ability. This is because, when it has a micelle forming ability, it has a drawback that the viscosity of the ink remarkably increases when the concentration exceeds 1% because the interaction between molecules is strong.

Among the compounds represented by the general formula (1), preferable examples include polyhydric alcohol ether derivatives and aliphatic 1,2-diols having 4 to 8 carbon atoms, such as ethylene glycol monobutyl ether. (Butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, 1,
A compound selected from 2-hexanediol and 1,2-pentanediol is more preferable. More preferred is triethylene glycol monobutyl ether or 1,2-hexanediol.

As the other hydrophilic solvent that can be used in the present invention, a water-soluble organic solvent is preferable. Specifically, alcohols (eg, methanol, ethanol,
Propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc., polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol) , Dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, tri Ethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dimethyl ether, etc.), amines For example, ethanolamine, diethanolamine, triethanolamine, N- methyldiethanolamine, N- ethyldiethanolamine, morpholine, N- ethylmorpholine, ethylenediamine,
Diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-)
Dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-). Examples thereof include imidazolidinone), sulfoxides (eg dimethyl sulfoxide), sulfones (eg sulfolane etc.), sulfonates (eg 1-butanesulfonic acid sodium salt etc.), urea, acetonitrile, acetone and the like.

The invention according to claim 6 is characterized in that the content of the hydrophilic solvent in the pigment ink is 5 to 70% by mass, preferably 10 to 60% by mass, particularly preferably 20 to 20% by mass. It is 50% by mass.

The invention according to claim 2 is characterized in that the redispersion coefficient represented by the above formula (1) of the pigment particles in the aqueous solvent is 3 or less.

The redispersion coefficient referred to in the present invention is a scale showing the dispersion stability and cohesiveness of the pigment particles, and as represented by the above formula (1), the volume average particles of the pigment particles before redispersion are obtained. It is represented by the ratio of the volume average particle size of the pigment particles after redispersion to the particle size. The volume average particle diameter in the present invention is a value measured by the secondary particle diameter.

Specifically, the volume average particle diameter of the pigment particles before redispersion represents the secondary particle diameter of the prepared pigment ink, and the volume average particle diameter of the pigment particles after redispersion means that the pigment ink was dried. The secondary particle size of the pigment particles after the dried pigment particles are added and deflocculated in a pigment ink medium such as water or an organic solvent, and the smaller the redispersion coefficient represented by the formula (1), the smaller Shows that the peptizing property and the dispersibility are excellent, and that the generation of aggregates is small, and the redispersion coefficient of 1 means that the secondary particle diameter does not change before and after the redispersion.

As a specific measuring method, 1 ml of the pigment ink is sampled, spread evenly on a washed petri dish, then left at room temperature and normal humidity for 1 week and dried. Then, 1 ml of water was added to the dried product, and the mixture was stirred and redispersed for 2 minutes using a glass rod, and the volume average particle diameter of the pigment particles in the pigment solution before and after drying was measured by the following method. To measure.

The volume average particle diameter can be measured by a commercially available particle size measuring instrument using, for example, a light scattering method, an electrophoresis method, a laser Doppler method or the like. Specific particle size measuring devices include, for example, a laser diffraction particle size measuring device SLAD1100 manufactured by Shimadzu Corporation, a particle size measuring device (HO
RIBA LA-920), Zetasizer 1000 manufactured by Malvern Company, and the like.

The present invention is characterized by a redispersion coefficient of 3 or less, preferably 1 to 3, more preferably 1 to 2, and particularly preferably 1 to 1.5.

In the present invention, the means for adjusting the redispersion coefficient to the range defined above is not particularly limited, but for example, the pigment particles having a polar group on the surface according to the present invention, the pigment according to the present invention may be used. Coating the surface with a polymer compound, optimizing the type and amount of surfactant added,
A desired redispersion degree can be obtained by appropriately selecting or combining various means such as controlling the secondary particle size distribution of the pigment particles and optimizing the pigment dispersing means and its dispersing conditions.

The invention according to claim 3 is characterized in that the secondary volume average particle diameter of the pigment particles is 10 to 90 nm, preferably 20 to 70 nm, particularly preferably 20.
It is ˜50 nm, and the volume average particle diameter defined in the present invention is preferable because the effects of the present invention can be exhibited at all.

In the present invention, the method for obtaining the pigment particles having the secondary volume average particle diameter defined above is not particularly limited, but, for example, the dispersing agent, dispersing means, dispersing conditions, etc. at the time of dispersing the pigment particles are selected. To obtain pigment particles having a desired secondary volume average particle diameter by selecting appropriately, or using self-dispersing pigments or using pigment particles whose surface is coated with a polymer resin, and optimizing the production conditions. You can

Examples of the pigment dispersant usable in the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, Polyoxyalkylene alkyl ether phosphate,
Activator such as polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivative, vinylnaphthalene derivative, acrylic acid, acrylic acid derivative And block copolymers, random copolymers and salts thereof composed of two or more kinds of monomers selected from maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives. You can

As the dispersing means that can be used in the present invention, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer,
Various dispersers such as a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill and a paint shaker can be used. Further, it is also preferable to use a centrifugal separator and a filter for the purpose of removing coarse particles of the pigment dispersion.

In the invention according to claim 4, the invention according to claim 1
Is characterized in that the static surface tension of the pigment ink for inkjet specified by 3 to 3 is 25 to 45 mN / m,
It is preferably 30 to 40 mN / m. As the means for adjusting the surface tension of the pigment ink of the present invention, it is preferable to appropriately adjust the type and amount of addition using the above-mentioned various ink solvents and the below-mentioned various surfactants.

The method of measuring the static surface tension is described in reference books on general surface chemistry and colloid chemistry. For example, New Experimental Chemistry Course Vol. 18 (Interface and colloid), Japan. Published by Maruzen Co., Ltd. 68 to 117, and specifically, the ring method (Duneuy method) and the vertical plate method (Wilhelmy method) can be used.

Further, in the invention according to claim 5,
It is characterized in that the pH of the pigment ink for inkjet specified by 4 to 4 is 7.0 or more, but preferably 8.
It is 0-10.0. Examples of the pH adjuster used in the aqueous medium used in the pigment ink of the present invention include various organic amines such as monoethanolamine, diethanolamine and triethanolamine, sodium hydroxide, lithium hydroxide, potassium hydroxide and the like. Examples thereof include inorganic alkali agents such as hydroxides of alkali metals, organic acids, and mineral acids.

The invention according to claim 7 is characterized in that the content of polyvalent metal ions in the pigment ink is 5 ppm or less, preferably 0.1 to 3 ppm, particularly preferably 0.1 to 1 ppm. Is. In the present invention, by setting the content of the polyvalent metal ion in the pigment ink to the amount defined above, a pigment ink having high gloss and transparency can be obtained.

The polyvalent metal ion referred to in the present invention means, for example, Fe ³⁺ , Sr ²⁺ , Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Z.
^Examples thereof include r ²⁺ , Ni ²⁺ and Al ³⁺ , which are contained as sulfates, chlorides, nitrates, acetates, organic ammonium salts, EDTA salts and the like.

In the pigment ink of the present invention, an anionic surfactant is used in the invention of claim 8, a nonionic surfactant is used in the invention of claim 9, and a cationic surfactant is used in the invention of claim 10. The invention according to claim 11 is characterized by containing an anionic surfactant and a nonionic surfactant.

The surfactant which can be used in the present invention is not particularly limited, but examples thereof include anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, fatty acid salts, and polyoxyethylene alkyl ethers. , Nonionic surfactants such as polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. To be In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

In the present invention, a polymeric surfactant can also be used, and examples thereof include styrene-acrylic acid-alkyl acrylate copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic. Acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic Examples thereof include acid copolymers and vinylnaphthalene-maleic acid copolymers.

The invention according to claim 12 is characterized in that the pigment ink contains a water-soluble polymer.

As a preferable example of the water-soluble polymer, a natural polymer can be cited. Specific examples thereof include glue,
Proteins such as gelatin, casein, or albumin, natural gums such as gum arabic, or gum tragacanth, glucosides such as savonine, alginic acid and propylene glycol alginate, triethanolamine alginate, or alginate derivatives such as ammonium alginate, methylcellulose, Examples thereof include cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, or ethyl hydroxyl cellulose.

Further, as a preferable example of the water-soluble polymer, a synthetic polymer can be mentioned, and polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymers, potassium acrylate-acrylonitrile copolymers. Acrylic resins such as vinyl acetate-acrylic acid ester copolymers or acrylic acid-acrylic acid ester copolymers, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid Ester copolymer, styrene-
Styrene acrylic acid resin such as α-methylstyrene-acrylic acid copolymer or styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer Such as polymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, etc. Examples thereof include vinyl acetate copolymers and salts thereof. Of these, polyvinylpyrrolidones and polyvinyl alcohols are particularly preferable.

The weight average molecular weight of the water-soluble polymer is 1,0.
It is preferably from 00 to 200,000. Furthermore, 3,
000 or more and 20,000 or less are more preferable. 1,00
If it is less than 0, the effect of suppressing the growth and aggregation of pigment particles is reduced, and if it exceeds 200,000, problems such as viscosity increase and poor dissolution tend to occur.

The amount of the water-soluble polymer added is 1 with respect to the pigment.
It is preferably 0% by mass or more and 1,000% by mass or less. Furthermore, 50 mass% or more and 200 mass% or less are more preferable.
If it is less than 10% by mass, the effect of suppressing the growth and aggregation of the pigment particles is reduced, and if it exceeds 1000% by mass, problems such as viscosity increase and poor dissolution tend to occur.

In the invention according to claim 13, the pigment particles are
It is characterized by having polar groups on the surface.

The term "pigment particles having a polar group on the surface" as used in the present invention means a pigment obtained by directly modifying the surface of a pigment particle with a polar group.
Alternatively, it refers to an organic substance having an organic pigment mother nucleus, to which polar groups are bonded directly or through a joint (hereinafter referred to as a pigment derivative).

As the polar group, for example, a sulfonic acid group,
Examples thereof include a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a sulfonic acid group.

In the present invention, as a method for obtaining pigment particles having a polar group on the surface, for example, WO97 / 487 is used.
69, JP-A-11-57458, 11-
No. 189739, JP-A 2000-265094, etc., a method of modifying the surface of pigment particles with a sulfonating agent, an oxidizing agent, etc., JP-A No. 11-49974, JP-A No. 2000-273383, 2000- 3030
Japanese Patent Application No. 2000-377, in which the pigment derivative described in JP-A No. 14 and the like is adsorbed on the surface of pigment particles by a treatment such as milling.
068, 2001-1495, 2001-2349.
After dissolving the pigment described in 66 together with the pigment derivative in a solvent, crystallization in a poor solvent can be mentioned.
By either method, pigment particles having a polar group on the surface can be easily obtained.

In the present invention, the polar group may be free or in the form of a salt, or may have a counter salt. Examples of the counter salt include inorganic salts (lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium), organic salts (triethylammonium, diethylammonium,
(Pyridinium, triethanolammonium, etc.), and a counter salt having a monovalent valence is preferable.

When the pigment surface is directly modified, it is preferably modified in the range of 0.1 to 50%, more preferably 0.1 to 20% of the pigment surface molecule.

When the pigment derivative is used, the addition amount is preferably 0.1 mol% or more and 50 mol% or less with respect to the pigment. If it is less than 0.1 mol%, the effect of suppressing the growth and aggregation of pigment particles is reduced, and if it exceeds 50 mol%, the expected effect cannot be obtained.

The invention according to claim 14 is characterized in that the surface of the pigment particle is coated with a polymer compound.

The pigment particles whose surface is coated with a polymer compound (hereinafter, also referred to as a polymer) referred to in the present invention include, for example,
Particles coated with a polymer compound having a pigment particle as a core and a surface thereof as a shell, or particles coated with a polymer compound having a pigment particle-containing polymer compound core as a surface and a surface thereof as a shell Can be mentioned.

The pigment particles whose surface is coated with the polymer compound according to the present invention can be prepared by various methods described below.

For example, a method of dispersing pigment particles described in JP-A-8-71405 with a polymer compound, dissolving the polymer compound in an organic solvent, and then phase inversion emulsifying in water, Journal of Coloring Materials, 70, 503 (1997), the method of polymerizing after adsorbing a monomer on the surface of pigment particles, Journal of Coloring Materials, 69, 743 (1996) and 72, 748.
The method of introducing a polymerization initiator to the surface of the pigment particle described in (1999) and then polymerizing it with a monomer can be mentioned.

In each of the above-mentioned methods, the polymer compound that can be used in the method of dissolving the polymer compound in which the pigment is dispersed in the organic solvent and then phase inversion emulsifying in water is used. , --COOH, --SO ₃ H), which is soluble in an organic solvent in an acid form and which is increased in hydrophilicity by being neutralized by a basic substance such as alkali or amine. Specific examples thereof include acrylic resin, styrene resin, polyester resin, epoxy resin, polyurethane resin, and the like, and acrylic resin and styrene resin are preferable.

As a method of polymerizing after adsorbing the monomer on the surface of the pigment particle, the pigment, the polymer containing the polar group and the hydrophobic monomer are added to the water-containing liquid, and the monomer is adsorbed for a certain period of time, and then the polymerization is started. It can be obtained by adding an agent and polymerizing for a certain period of time.

Examples of the polar group-containing monomer that can be used in the above method include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid,
Monobutyl itaconate, monobutyl maleate, acid phosphooxyethyl methacrylate, acid phosphooxypropyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl methacrylate, vinyl Examples thereof include sodium sulfonate and the like.

As the hydrophobic monomer, for example, various styrenic monomers (aromatic vinyl monomers) such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene or chlorostyrene; methyl acrylate, Ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-acrylate
Various acrylates such as hexyl, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate or dodecyl acrylate; methyl methacrylate, propyl methacrylate, n-methacrylate
Various methacrylates such as butyl, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, decyl methacrylate or dodecyl methacrylate; hydroxy acrylate Various hydroxyl group-containing monomers such as ethyl or hydroxypropyl methacrylate; or N
Various types of N-, such as methylol (meth) acrylamide or N-butoxymethyl (meth) acrylamide
Substituted (meth) acrylic monomers are included.

As the polymerization initiator which can be used,
There is no particular limitation, and for example, benzoyl peroxide, di-t-
Butyl peroxide, cumene hydroperoxide, t-
There may be mentioned various peroxides such as butyl peroxide or 2-ethylhexanoate; or various azo compounds such as azobisisobutyronitrile or azobisisovaleronitrile.

Further, as a method of introducing a polymerization initiator to the surface of the pigment particle and then polymerizing it together with the monomer, a functional group (eg, amino group, hydroxyl group) of the pigment is chemically reacted with a peroxide group such as a peroxycarbonyl group. And a method of introducing a group that initiates polymerization from the carboxyl group by generating a carboxyl group on the pigment surface with an oxidizing agent such as hypochlorous acid. A polymer-coated pigment can be obtained by polymerizing the above-mentioned hydrophobic monomer and polar group-containing monomer with the pigment having a polymerization initiation group on the surface obtained by these methods.

In the present invention, the coating amount of the polymer compound on the pigment is 1% or more and 100% or less, preferably 5% or more and 50% or less.

In the present invention, the above-mentioned pigments are preferably blended in the pigment ink in an amount of 1 to 30% by mass, more preferably 1.5 to 25% by mass. If the content of the above pigment is less than 1% by mass, the printing density is insufficient, and if it exceeds 30% by mass, the stability of the suspension over time is deteriorated and the particle size tends to increase due to aggregation and the like. It is preferable to set the inside.

In addition to the above description, the pigment ink of the present invention may be used in accordance with the purpose of improving emission stability, compatibility with print heads and ink cartridges, storage stability, image storability, and other performances, if necessary. , Various known additives,
For example, a viscosity modifier, a specific resistance modifier, a film-forming agent, an ultraviolet absorber, an antioxidant, an anti-fading agent, a fungicide, an anticorrosive agent, etc. can be appropriately selected and used, for example, liquid paraffin, Oil droplet fine particles such as dioctyl phthalate, tricresyl phosphate, and silicone oil, JP-A-57-7
No. 4193, No. 57-87988 and No. 62-261.
UV absorbers described in JP-A-57-7419.
No. 2, No. 57-87989, No. 60-72785,
No. 61-146591, JP-A-1-95091 and JP-A-3-13376, and anti-fading agents, JP-A-59-42993, JP-A-59-52689, and JP-A-59-52689.
2-280069, 61-242871, JP-A-4-219266, and the like can be cited as a brightening agent.

The recording medium used in the present invention includes plain paper, coated paper, swelling type inkjet recording paper provided with an ink receiving layer which absorbs an ink liquid and swells, and voids having a porous ink receiving layer. Type inkjet recording paper,
Further, a resin support such as a polyethylene terephthalate film may be used instead of the base paper, but it is preferable to use a void type porous inkjet recording medium as the recording medium. Most effective.

As the porous ink jet recording medium,
Specifically, mention may be made of void-type inkjet recording paper or void-type inkjet film, which are recording media provided with a void layer having an ink absorbing ability, and the void layer is mainly hydrophilic. It is formed by soft agglomeration of the binder and the inorganic fine particles.

Various methods for forming a void layer are known as a method for forming voids in a film. For example, a uniform coating solution containing two or more kinds of polymers is coated on a support and dried in a drying process. A method of phase-separating these polymers with each other to form voids, a coating liquid containing solid fine particles and a hydrophilic or hydrophobic binder is applied on a support, and after drying,
A method of immersing an inkjet recording paper in water or a liquid containing a suitable organic solvent to dissolve solid fine particles to form voids, a coating liquid containing a compound having a property of foaming during film formation, and a drying process. A method of foaming this compound to form voids in the film, a method of applying a coating liquid containing porous solid fine particles and a hydrophilic binder onto a support to form voids in the porous fine particles or between the fine particles. ,
A method of forming voids between solid fine particles by applying a coating liquid containing solid fine particles and / or fine particle oil droplets and a hydrophilic binder having a volume equal to or more than the hydrophilic binder to a solid fine particle. However, when using the ink of the present invention, good results are obtained even if they are provided by any method.

The inkjet head that can be used in the inkjet image recording method of the present invention may be either an on-demand system or a continuous system.
In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type,
Bender type, piston type, shear mode type, shared wall type, etc., electric-heat conversion method (for example, thermal ink jet type, bubble jet (R) type, etc.), electrostatic attraction method (for example, electric field control type, slit jet) Type) and a discharge method (for example, a spark jet type) can be given as specific examples, but any discharge method may be used.

[0111]

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 << Preparation of Pigment Dispersion >> (Preparation of Magenta Pigment Dispersion 1) C.I. I. Pigment Red 122 166 g <Polymer 1> (Monomer composition ratio: styrene / 2-ethylhexyl acrylate / n-butyl acrylate / methacrylic acid = 59/11/15/15) 32 g Diethylene glycol 180 g Ion-exchanged water 1000 g The above additives were mixed. Then, it was dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads in a volume ratio of 60%. Then, the mixture was diluted with ion-exchanged water to a pigment concentration of 5% by mass, and then centrifuged. Next, the supernatant liquid was repeatedly concentrated and watered using an ultrafiltration device, and desalted until the electric conductivity became 2000 μS / cm or less to prepare a magenta pigment dispersion liquid 1.

(Preparation of Magenta Pigment Dispersion Liquid 2) Magenta Pigment Dispersion Liquid 2 was prepared in the same manner as in Preparation of Magenta Pigment Dispersion Liquid 1 described above, except that Polymer 2 was used instead of Polymer 1.

<Polymer 2> Monomer composition ratio: styrene / 2-ethylhexyl acrylate / n-butyl acrylate / styrene sulfonic acid = 64/16/15/5 (Preparation of magenta pigment dispersion liquid 3: self-dispersion pigment) 6 mol / After adding 1.5 g of anthranilic acid to 10 g of L hydrochloric acid solution, the mixture was cooled to 5 ° C, 1.8 g of sodium nitrite was added, and the mixture was stirred. C. there. I. Pigment Red 12
2 (Clariant PV Fast Pink EB-
5 g of (trans) powder, and the liquid temperature is 8 while stirring.
The temperature was raised to 0 ° C., the heating was continued until the generation of nitrogen gas disappeared, and then the system was cooled. Next, acetone was added to filter and wash the pigment particles, and then each operation of ion exchange, ultrafiltration and centrifugation was performed to obtain a magenta pigment dispersion liquid 3.

(Preparation of Magenta Pigment Dispersion Liquid 4: Self-Dispersion Pigment) Magenta Pigment Dispersion Liquid 4 was prepared in the same manner as in Magenta Pigment Dispersion Liquid 3 except that the same amount of sulfanilic acid was used instead of anthranilic acid. Was prepared.

(Preparation of Magenta Pigment Dispersion Liquid 5: Self-Dispersion Pigment) Magenta Pigment Dispersion Liquid 5 was prepared in the same manner as in Magenta Pigment Dispersion Liquid 4 above, except that the centrifugation operation was not performed.

(Preparation of Magenta Pigment Dispersion Liquid 6: Self-Dispersion Pigment) C.I. I. Pigment Red 122 100 g Sulfoquinacridone 8 g Ion-exchanged water 1000 ml The above additives were mixed and then dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60%. Then, the mixture was diluted with ion-exchanged water to a pigment concentration of 5% by mass, and then centrifuged. Then, the supernatant liquid was subjected to removal and concentration of unadsorbed sulfoquinacridone using an ultrafiltration device, and then subjected to a centrifugation step to prepare a magenta pigment dispersion liquid 6.

(Preparation of Magenta Pigment Dispersion Liquid 7: Self-Dispersion Pigment) C.I. I. Pigment Red 122 30 g Sulfodimethylquinacridone 1.95 g Polyvinylpyrrolidone 100 g Dimethyl sulfoxide 2000 g 10% sodium hydroxide solution 500 ml After mixing and dissolving each of the above additives, the solution was electrofiltered into 2000 ml of ion exchange water by ultrafiltration. Conductivity 20
Concentrate and add water at the same time until it becomes less than 00 μS / m,
Then, the solution is centrifuged at 50 ml / min.
Magenta Pigment Dispersion Liquid 7 was prepared.

(Preparation of Magenta Pigment Dispersion Liquid 8: Self-Dispersion Pigment) In the above-mentioned preparation of magenta pigment dispersion liquid 7, C.I.
I. Pigment Red 122 was added in an amount of 100 g and sulfodimethylquinacridone was added in an amount of 6.5 g to prepare Magenta Pigment Dispersion Liquid 8 in the same manner.

(Preparation of Magenta Pigment Dispersion Liquid 9: Self-Dispersion Pigment) In the preparation of Magenta Pigment Dispersion Liquid 8 described above, instead of polyvinylpyrrolidone, the following surfactant SA-
Magenta Pigment Dispersion Liquid 9 was prepared in the same manner except that 1 was used.

SA-1: C ₁₂ H ₂₅ PhO (CH ₂ CH
₂ O) ₁₅ H (nonionic surfactant) (Preparation of magenta pigment dispersion liquid 10: resin-coated pigment) 22
g of Polymer 1 and 100 g of C.I. I. Pigment Red 122 in 3000 g of methyl ethyl ketone,
Dispersion was performed by using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to prepare a dispersion liquid. Next, 100 g of n-butanol was added to this dispersion, and the pH was adjusted to 7.0 with a 1 mol / L sodium hydroxide solution.
Adjusted to. Next, this dispersion liquid was dropped into ion-exchanged water with a dropping funnel, methyl ethyl ketone and n-butanol were removed under reduced pressure, and then centrifugal separation operation was performed to prepare magenta pigment dispersion liquid 10.

(Preparation of Magenta Pigment Dispersion Liquid 11: Resin Coated Pigment) In the preparation of magenta pigment dispersion liquid 10,
A magenta pigment dispersion liquid 11 was prepared in the same manner except that the following polymer 3 was used in place of the polymer 1.

<Polymer 3> Monomer composition ratio: styrene / 2-ethylhexyl acrylate / n-butyl acrylate / methacrylic acid / sodium styrenesulfonate = 59/11/15/15 /
1 (Preparation of magenta pigment dispersion 12: resin-coated pigment) C.I. I. Pigment Red 122 3 g Pyridine 2 ml Adipic dichloride 2 ml Tetrahydrofuran 100 ml The above mixture was reacted at 60 ° C. for 2 hours under a nitrogen stream. Then, the pigment reaction product was separated by filtration, and 20 ml of t-butyl hydroperoxide and 0.4
g of sodium hydroxide was added, and the mixture was reacted under a nitrogen stream at room temperature for 24 hours. Then, the reaction product was filtered off and washed with tetrahydrofuran, and then 30 ml of tetrahydrofuran and 1.5 g of the following monomer 1 were added to the reaction product.
The reaction was carried out at 0 ° C for 6 hours. Ion-exchanged water was added to the polymerization reaction product in an appropriate amount, and the pH was adjusted to 7.0 with diethanolamine. After repeating concentration and water addition by ultrafiltration, centrifugation was performed to prepare a magenta pigment dispersion liquid 12. did.

<Monomer 1> Composition ratio: styrene / 2-ethylhexyl acrylate /
n-butyl acrylate / acrylic acid / sodium styrenesulfonate = 64/16/15/15/1 (Preparation of Magenta Pigment Dispersion Liquid 13: Resin Coated Pigment) Dioctyl sodium sulfosuccinate dispersed in C.I.
I. Pigment Red 122 10% by mass aqueous dispersion 1
After adding an additive containing the following monomer 2 to 0 g, 80
The polymerization reaction was carried out at 6 ° C for 6 hours.

<Monomer 2> (Composition ratio: styrene / 2-ethylhexyl acrylate / methacrylic acid = 64/16/15) 2 g Ethanol 5 g Potassium persulfate 0.01 g After the polymerization reaction, concentration and ultrafiltration were repeated by ultrafiltration. After that, a centrifugation operation was performed to prepare a magenta pigment dispersion liquid 13.

(Preparation of Magenta Pigment Dispersion Liquid 14: Resin Coated Pigment) In the preparation of magenta pigment dispersion liquid 13,
A magenta pigment dispersion liquid 14 was prepared in the same manner except that the centrifugation operation was not performed.

(Preparation of Magenta Pigment Dispersion Liquid 15: Resin Coated Pigment) In the preparation of magenta pigment dispersion liquid 13,
A magenta pigment dispersion liquid 15 was prepared in the same manner except that the following monomer 3 was used in place of the monomer 2.

<Monomer 3> Composition ratio: styrene / 2-ethylhexyl acrylate /
Methacrylic acid / styrene sulfonic acid = 64/16/20
/ 1 (Preparation of Magenta Pigment Dispersion Liquid 16: Resin-Coated Pigment) Magenta pigment dispersion liquid 16 was prepared in the same manner as in the preparation of magenta pigment dispersion liquid 15, except that the centrifugation operation was not performed.

The details of each magenta pigment dispersion prepared as described above are summarized in Table 1.

[0130]

[Table 1]

<< Preparation of Pigment Ink >> Then, magenta pigment inks 1 to 42 were prepared using the magenta pigment dispersions 1 to 16 prepared above.

In each magenta pigment dispersion liquid, pure water, the ink solvent shown in Tables 2 and 3, a polyvalent metal ion aqueous solution,
Each magenta pigment ink was prepared by adding a surfactant and a polymer compound so as to have the concentrations shown in Tables 2 and 3.
Further, the addition amount of each magenta pigment dispersion liquid was appropriately adjusted so that the pigment concentration in the pigment ink was 3% by mass. When the pigment concentration in the magenta pigment dispersion liquid is insufficient and the pigment concentration in the pigment ink cannot be adjusted to 3%, the pigment dispersion liquid was concentrated under reduced pressure by removing water.

Specific compounds of the additive abbreviations shown in Tables 2 and 3 are as follows. The following composition was used as the ink solvent for the pigment ink. In addition, each numerical value represents the mass% with respect to the ink.

(Solvent) Solvent species 1: ethylene glycol (EG) / glycerin (gly) / triethylene glycol monobutyl ether (TEGBE) = 10/10/10 Solvent species 2: ethylene glycol (EG) / glycerin (gly) / Triethylene glycol monobutyl ether (TEGBE) = 3/1/8 Solvent type 3: ethylene glycol (EG) / glycerin (gly) / triethylene glycol monobutyl ether (TEGBE) = 25/10/30 (polyvalent metal ion) As the polyvalent metal ion aqueous solution, a 0.1% aqueous solution of ferric chloride was used as iron ions, and the concentrations were adjusted to the concentrations shown in Tables 2 and 3. The pH is 0.1 mol / L of nitric acid aqueous solution or sodium hydroxide aqueous solution, and the pH values shown in Table 4 and Table 5 below are used.
It was adjusted to be H.

(Latex) The details of the latex are as follows. All numerical values are molar ratios.

Lx-1: n-butyl acrylate / methyl methacrylate / Aqualon RN-20 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) = 50/50/5 average particle diameter; 60 nm average zeta potential; -18 mV Lx-2: n- Butyl acrylate / methyl methacrylate / acrylic acid = 50/50/5 average particle size; 60
nm average zeta potential; -35 mV Lx-3: n-butyl acrylate / methyl methacrylate / acrylic acid / sodium styrenesulfonate = 5
0/50/2/5 average particle diameter; 60 nm average zeta potential; -52 mV Lx-4: n-butyl acrylate / methyl methacrylate / acrylic acid / Aquaron HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) = 50/50 / 2/5 average particle diameter; 60 nm
Average zeta potential; -65 mV Lx-5: n-butyl acrylate / methyl methacrylate / acrylic acid = 50/50/5 average particle size; 12
0 nm average zeta potential: -35 mV <Synthesis example of latex> The synthesis example of latex Lx-2 is shown below.

To a polymerization vessel equipped with a stirrer and a heat retaining jacket, 1000 parts of ion-exchanged water was added, and the mixture was vigorously stirred while introducing nitrogen. Then, after completely replacing the air in the vessel with nitrogen, the solution temperature was raised to 60 ° C., and 0.1 parts by mass of ammonium persulfate as a polymerization initiator was added to Na ₂ CO ₃
5 parts by mass and 0.1 part by mass of sulfosuccinic acid di (2-ethylhexyl) sodium salt were added. Then, 50 parts by mass of n-butyl acrylate and 5 parts of methyl methacrylate are used.
0 parts by mass and 2 parts by mass of acrylic acid were added dropwise, and after the completion, 3 parts by mass of acrylic acid was added. Then, after stirring for 2 hours to complete the polymerization, neutralization, centrifugation and ultrafiltration were performed to remove the residual surfactants and the like, and the latex L
x-2 was prepared.

Regarding the other latices, the latices having the above-mentioned constitution, particle size and zeta potential were prepared by appropriately changing the kind of the monomer, the salt concentration, the amount of the surfactant or the stirring speed.

(Other Additives) SA-2: Surfynol 465 (manufactured by Nisshin Chemical Industry Co., Ltd.)
Nonionic surfactant) SA-3: Di (2-ethylhexyl) sulfosuccinate sodium salt (anionic surfactant) P-1: Johncryl 61J (water-soluble acrylic polymer: manufactured by Johnson Polymer Co., Ltd.) P-2: Polyvinyl Alcohol (manufactured by Kuraray Co., Ltd.) (Measurement of average zeta potential of latex) The zeta potential of particles in each latex was measured by using ELS-800 (manufactured by Otsuka Electronics Co., Ltd.) after diluting the latex solution by 1000 times. , 500 particles were measured, and the average value was obtained.

(Measurement of Average Zeta Potential of Pigment Particles) The pigment ink liquid was diluted 1000 times and then ELS-800.
(Manufactured by Otsuka Electronics Co., Ltd.) was used to measure 500 particles, and the average value was obtained.

(Measurement of Secondary Average Particle Diameter of Pigment Ink) Each pigment ink prepared above was diluted 1000 times, and then secondary particle diameter was measured using Zetasizer 1000 manufactured by Malvern Instruments.

Details of the constitution and characteristic values of the pigment ink prepared as described above are shown in Tables 2 and 3.

[0143]

[Table 2]

[0144]

[Table 3]

<< Measurement of Characteristic Value of Each Pigment Ink >> The following characteristic values were measured for each of the pigment inks prepared above, and the obtained results are shown in Tables 4 and 5 below.

<Measurement of Static Surface Tension> The static surface tension of each ink prepared above was measured by the vertical plate method (Wilhelmy method).

<Measurement of pH> The pH was measured by a conventional method.

<Measurement of Redispersion Coefficient> After collecting 1 ml of each ink and spreading the ink evenly on a washed dish,
Leave at room temperature and humidity for 1 week to dry. Next, 1 ml of water was added to the dried product, and the mixture was stirred and redispersed for 2 minutes using a glass rod, and the volume average particle size of the pigment particles in the ink before and after the redispersion was measured by the following method. It was measured.

The volume average particle diameter was measured by diluting each ink before and after drying 1000 times and then using Zetasizer 1000 manufactured by Malvern Instruments Ltd., and the redispersion coefficient was obtained according to the above formula (1).

<< Formation and Evaluation of Magenta Image >> (Image Output) After each magenta pigment ink obtained was stored in an ink cartridge, the nozzle hole diameter was 20 μm, the driving frequency was 12 kHz, the number of nozzles per color was 128, and the nozzles of the same color were used. Konica Corporation uses an on-demand inkjet printer with a maximum recording density of 720 x 720 dpi equipped with a piezo type head with a density of 180 dpi.
Inkjet Paper Made Images Photographs QP and plain paper were printed with images 1 to 46 in the combinations shown in Tables 4 and 5. The term "dpi" used in the present invention means 2.54 cm
The number of dots per (1 inch). As the output image, a wedge image obtained by dividing the output density from 0% to 100% in 16 steps (outputted in a patch shape of 3 cm × 3 cm for each density) was used. In addition, the same image data,
Digital Minilab QD-21 PLUS (manufactured by Konica) was used to output on Konica Color QA Paper Type A7, which was subjected to development processing to prepare a color silver salt photographic image for comparison, and the following evaluation was performed.

(Evaluation of light resistance) Regarding light resistance, a wedge image having a reflection density of about 1.0 was used, and after irradiating 70,000 lux of xenon light for 240 hours in a xenon fade meter, The residual rate {(reflection density after irradiation with xenon light) ÷ (reflection density before irradiation with xenon light) × 100 (%)} was calculated.

(Evaluation of Scratch Resistance) With respect to a wedge image having a reflection density of about 1.0, it was visually judged whether or not stains were generated on the printed portion when the wedge image was rubbed 10 times with an eraser (MONO Dragonfly Pencil Co., Ltd.). .

◯: No stain on the printed part is observed. Δ: Some stain on the printed part is observed. X: Stain on the printed part is clearly observed (evaluation of glossiness). In order to determine whether or not gloss was obtained, the wedge image prepared above was compared and evaluated with the color silver salt photographic image for comparison prepared at the same time. The evaluation was carried out by visual evaluation by 20 general evaluators and judged according to the following criteria.

5: 18 or more people were evaluated as equivalent to the silver salt photograph 4: 15 to 17 people were evaluated as equivalent to the silver salt photograph 3: 11 people were evaluated as equivalent to the silver salt photograph 14 people 2: 8 people evaluated to be equivalent to silver salt photograph: 10 people 1: 7 people or less evaluated to be equivalent to silver salt photograph (evaluation of transparency) Regarding transparency, the image was silver salt. In order to determine whether or not a transparency equivalent to that of a photograph was obtained, the wedge image prepared above was compared and evaluated with a color silver salt photographic image for comparison prepared at the same time. The evaluation was carried out by visual evaluation by 20 general evaluators and judged according to the following criteria.

[0155] 5: 18 or more people evaluated as equivalent to silver salt photograph 4: 15 to 17 people evaluated as equivalent to the silver halide photograph. 3: 11 to 14 people evaluated as equivalent to the silver halide photograph. 2: 8 to 10 people evaluated as equivalent to the silver halide photograph. 1: 7 people or less evaluated as equivalent to silver salt photograph The evaluation results obtained as described above are shown in Tables 4 and 5.

[0156]

[Table 4]

[0157]

[Table 5]

As is clear from Tables 4 and 5, the pigment ink in which the absolute value of the average zeta potential of the latex of the present invention is smaller than the absolute value of the average zeta potential of the pigment particles is a color silver salt as compared with the comparative example. It can be seen that it has glossiness and transparency equal to or higher than that of a photographic image, and is excellent in light resistance and scratch resistance. Further, the effect of the present invention is to use self-dispersed pigment particles or resin-coated pigment particles as a pigment, to adjust pH, particle diameter of pigment particles, and zeta potential within the ranges specified in the present invention, and to use a surfactant. It was confirmed that the effect was further exerted by controlling the amount of polyvalent metal ion to be less than the specified amount, controlling the amount of the ink solvent, and using the water-soluble polymer.

Example 2 (Preparation of Pigment Ink Set) In accordance with the preparation method of the magenta pigment dispersion liquids 3, 4, and 15 prepared in Example 1, the yellow dispersion liquid was C.I. I. Pigment Yellow 128 and cyan dispersion liquid are C.I. I. Pigment Blue 5: 3, carbon black was used as the black dispersion, each color dispersion was prepared, and then the ink sets 1, 2, and 30 were prepared according to the method for preparing the pigment inks 6, 7, and 30 described in Example 1. 5, 6 were prepared.

In accordance with the method for preparing the magenta pigment dispersion liquid 8 prepared in Example 1, the yellow dispersion liquid was C.I. I.
Pigment Yellow 128, its sulfonated product, and a cyan dispersion liquid are C.I. I. Pigment Blue 15: 3 and sulfophthalocyanine (sulfonation rate: 1.5) were used to prepare pigment dispersions of each color. The black dispersion was prepared by appropriately mixing the yellow dispersion, the magenta dispersion and the cyan dispersion. Using each of these dispersions, ink sets 3 and 4 were prepared according to the method for preparing pigment inks 15 and 18 described in Example 1.

The difference between the absolute value of the average zeta potential of the pigment particles (| A |) and the absolute value of the average zeta potential of the latex (| B |) shown in Table 6 is the value | A | It was displayed in the range of the potential difference using the zeta potential value of.

<< Image Output and Evaluation >> (Image Output) After each of the obtained pigment ink sets 1 to 6 was housed in an ink cartridge, the nozzle hole diameter was 20 μm, the drive frequency was 12 kHz, the number of nozzles per color was 128, and the same color An on-demand inkjet printer with a maximum recording density of 720 x 720 dpi is used with a piezo head with a nozzle density of 180 dpi, and inkjet images 101-107 are printed on Konica K.K. inkjet photo paper QP or plain paper. Output.

As the output image, the output density is from 0% to 1
Wedge images (outputted in 3 cm x 3 cm patches for each density) divided into 16 steps from 00% and high-definition color digital standard image data "N5 / bicycle" issued by the Japan Standards Association (December 1995) Monthly issue) was used as the output image. Also, the same image was output on Konica Color QA Paper Type A7 using Digital Minilab QD-21 PLUS (manufactured by Konica) and developed to prepare a color silver salt photographic image for comparison. By the method described, light resistance, scratch resistance, glossiness, transparency, and comprehensive image quality evaluation described below were performed. The light resistance is shown by the average remaining rate of each color ink.

(Comprehensive image quality evaluation) The output image of the high-definition color digital standard image data "N5 / Bicycle" (issued in December 1995) issued by the Japan Standards Association, which was formed by the above method, was arbitrarily selected. Ten panelists were selected and the texture was evaluated by visual observation according to the following criteria. The visual distance at the time of evaluation is 300 to 400 mm,
The illuminance was 1000 ± 50 lux.

5: The output image has a texture, depth, and transparency, and has an image quality comparable to that of a photographic image. 4: The output image has a texture, depth, and transparency, and has an image quality similar to that of a photographic image. 3: The output image is slightly inferior in quality, depth, and transparency, and the image quality is slightly inferior to the photographic image. 2: Output image is inferior in texture, depth, and transparency, and the image quality is inferior to the photographic image. : The output image has no texture, depth, or transparency, and has an image quality far from that of the photographic image. For evaluation, the evaluation values of each panel were averaged and the values were rounded off.

Table 6 shows the results obtained as described above.

[0167]

[Table 6]

As is clear from Table 6, in the Y, M, C and K multicolor inks, the absolute value of the average zeta potential of the latex of the present invention is similar to that of the pigment particles, as in the case of Example 1. Pigment ink smaller than the absolute value of the average zeta potential,
Compared with the comparative example, the color silver salt photographic image has the same or more glossiness and transparency, and has improved light resistance and scratch resistance,
It can be seen that the overall image quality is excellent.

[0169]

INDUSTRIAL APPLICABILITY According to the present invention, an ink jet pigment ink having excellent glossiness and transparency of an ink jet recorded image and improved light resistance and scratch resistance, an ink jet cartridge using the same, an ink jet image recording method and an ink jet ink. We were able to provide the recorded images.

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Claims (17)

[Claims] 1. An inkjet pigment ink containing pigment particles, a hydrophilic solvent, water and a latex, wherein the absolute value of the average zeta potential of the latex is smaller than the absolute value of the average zeta potential of the pigment particles. Inkjet pigment ink. 2. The redispersion coefficient represented by the following formula (1) is 3
The pigment ink for inkjet according to claim 1, wherein: Formula (1) Redispersion coefficient = secondary volume average particle diameter of pigment particles after redispersion / secondary volume average particle diameter of pigment particles before redispersion 3. The secondary volume average particle diameter of the pigment particles is
It is 10-90 nm, 1 or 2 characterized by the above-mentioned.
The inkjet pigment ink according to item 1. 4. The ink jet pigment ink according to any one of claims 1 to 3, wherein the static surface tension is 25 to 45 mN / m. 5. The inkjet pigment ink according to any one of claims 1 to 4, which has a pH of 7.0 or more. 6. The inkjet pigment ink according to claim 1, wherein the content of the hydrophilic solvent is 5 to 70 mass%. 7. The inkjet pigment ink according to claim 1, wherein the polyvalent metal ion content is 5 ppm or less. 8. The inkjet pigment ink according to claim 1, further comprising an anionic surfactant. 9. The inkjet pigment ink according to claim 1, further comprising a nonionic surfactant. 10. The inkjet pigment ink according to claim 1, further comprising a cationic surfactant. 11. The inkjet pigment ink according to claim 1, further comprising an anionic surfactant and a nonionic surfactant. 12. The ink-jet pigment ink according to claim 1, further comprising a water-soluble polymer. 13. The inkjet pigment ink according to claim 1, wherein the pigment particles have a polar group on the surface. 14. The inkjet pigment ink according to claim 1, wherein the pigment particles have a surface coated with a polymer compound. 15. An ink jet cartridge comprising an ink containing portion containing at least one pigment ink for ink jet according to any one of claims 1 to 14. 16. An inkjet image recording method, comprising forming an image using at least one pigment ink for inkjet according to claim 1. 17. An inkjet recorded image formed by performing inkjet image recording using at least one pigment ink for inkjet according to any one of claims 1 to 14.