JP5236253B2 - Pigment dispersion, ink for ink jet recording, ink jet recording method, ink cartridge and ink jet recording apparatus - Google Patents

Description

  The present invention relates to a pigment dispersion, ink for ink jet recording (hereinafter sometimes simply referred to as “ink”), an ink jet recording method, an ink cartridge, and an ink jet recording apparatus. More specifically, a colorant dispersion type pigment dispersion having high storage stability, good fixability and fastness of a printed image, and suitable for inkjet recording, an aqueous inkjet recording ink, and an inkjet recording method using the ink The present invention relates to an ink cartridge and an ink jet recording apparatus.

  Conventionally, water-insoluble colorants such as pigments having excellent fastness such as water resistance and light resistance have been widely used as colorants for printing inks. However, in order to use the water-insoluble color material as the color material of the water-based ink, it is required to stably disperse the water-insoluble color material in the aqueous medium. Therefore, a color material dispersion type aqueous ink is used in which a dispersant such as a polymer compound or a surfactant is added to uniformly disperse a water-insoluble color material in an aqueous medium.

  In recent years, also in ink jet recording applications, this color material dispersion type aqueous ink has been used as an ink for ink jet recording from the viewpoint of image fastness. In ink jet recording, attempts have been made to give the colorant particles in the ink an aggregating function and a water insolubilizing function in order to improve the fixability of the ink on the paper surface and the water resistance of the recorded image. However, by imparting such a function to the color material particles, the dispersion stability of the color material in the ink is lowered, and the color material particles aggregate during storage of the ink, resulting in uneven density and sedimentation. There is a problem that clogging occurs due to drying of the ink at the nozzle tip portion of the ink jet apparatus, which tends to occur, and the ink ejection stability tends to decrease.

  In order to solve the above problems, Patent Documents 1, 2 and 3 propose block polymers having a specific acrylic monomer structure as a hydrophilic segment, but these polymers have hydrophilic properties constituting the polymer. Since the affinity of the monomer structure portion to the recording material is insufficient, the image fastness such as ink fixability and scratch resistance is not sufficiently satisfactory when the polymer is used in ink. Furthermore, there is a problem that the ejection stability of the ink containing the block polymer is greatly lowered in an application that requires long-term continuous printing in industrial applications.

Patent Document 4 proposes an ink containing a polymer dispersant and a urethane resin. However, the ink has a problem that the dispersion stability of the coloring material during long-term storage or high-temperature storage greatly decreases. In addition, the ejection stability of the ink is greatly reduced in applications where continuous printing over a long period of time is required in industrial applications. In addition, when such an ink is used in an ink jet recording apparatus in which the ink is ejected with thermal energy, there is a problem that the color material particles are intensively aggregated due to heat generation and the ink cannot be ejected.
JP-A-4-227668 JP-A-5-179183 JP 2005-177756 A JP 2006-282760 A

  The object of the present invention has been made in view of the above problems, and is capable of stably recording an image having high fastness such as fixability and scratch resistance and excellent quality in any case over a long period of time. Ink jet recording ink and ink jet recording method capable of recording an image having excellent fastness and quality, and an ink cartridge and an ink jet recording apparatus including such an ink are provided. There is.

（式中、Ｒ¹は水素原子またはメチル基を、Ｘは水素原子または炭素数１から４のアルキル基を表し、ｎは１から１０である。）

（式中、Ｒ ² は水素原子またはメチル基を、Ｙは−Ｒ ³ 、−ＯＲ ³ または−ＣＯＯＲ ³ を表す。ここでＲ ³ は炭素数１から１８のアルキル基を表す。） As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following invention.
That is, the present invention, the polymeric dispersing agents, pigments, and the predominantly pigment dispersion from the water, the pigment is encapsulated by the polymer dispersant, the polymer dispersant, and at least a hydrophobic unit The hydrophilic unit has a block part composed of at least one hydrophobic monomer, and the block part is a block part composed of a repeating unit structure of the following general formula (2), and the hydrophilic unit unit to provide a pigment dispersion, which is a copolymer having a repeating unit structure of an acrylamide structure of at least the following general formula (1).

(Wherein R ¹ represents a hydrogen atom or a methyl group, X represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is 1 to 10).

(In the formula, R ² represents a hydrogen atom or a methyl group, Y represents —R ³ , —OR ^3, or —COOR ³ , where R ³ represents an alkyl group having 1 to 18 carbon atoms.)

In the pigment dispersion of the present invention, the pigment is C.I. I. Pigment Yellow 3, 74, 93, 95, 109, 120, 128, 138, 151, 175, 183, 184; I. Pigment Red 12, 122, 184, 202; I. Pigment violet 19, 32; I. Pigment Blue 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16; I. Pigment green 7; and C.I. I. At least Tanedea Rukoto selected from the group consisting of pigment black 1,7,10,31,32; hydrophilic unit, it has a segment having an anionic hydrophilic group; hydrophilic unit, Having a block part composed of a repeating unit structure of the general formula (1) and a block part of a segment having an anionic hydrophilic group; the polymer dispersant is a repeating unit structure of the general formula (2) A block part consisting of a repeating unit structure of the general formula (1) and a block part of a segment having an anionic hydrophilic group; and calcium ions and / or magnesium ions These ions are in a total amount (A), and A: B is 1: 100000 or more with respect to the polymer dispersant (B). : It is preferably contained in a range of 100 following weight ratio. The A: B is more preferably in a mass ratio range of 1: 20000 to 1: 200.

  In addition, the present invention provides an ink for ink jet recording, wherein the pigment dispersion is mixed with at least a water-soluble organic solvent.

  Further, the present invention provides an ink jet recording method in which energy is applied to an ink, the ink is ejected and applied to a recording material, and the ink is the ink of the present invention. Provide a method. In the recording method, the energy is preferably thermal energy.

  According to another aspect of the present invention, there is provided an ink cartridge including an ink storage portion that stores ink, wherein the ink is the ink for ink jet recording according to the present invention; and an ink storage portion that stores the ink. An ink jet recording apparatus comprising an ink cartridge provided and a head unit for ejecting the ink, wherein the ink is the ink of the present invention.

  According to the present invention, it is possible to provide a pigment dispersion and an ink capable of stably recording an image having high fastness and excellent quality in any case over a long period of time. Ink and ink jet recording methods, ink cartridges, and ink jet recording apparatuses capable of recording images having excellent properties and quality can be provided.

（式中、Ｒ¹、Ｘ、ｎは前記定義の通りである。） Hereinafter, the present invention will be described in detail.
In the pigment dispersion mainly composed of a polymer dispersant, a pigment, and water, the present inventors comprise at least a hydrophobic unit and a hydrophilic unit as the polymer dispersant, and at least one hydrophobic unit. A copolymer having a block unit composed of a hydrophobic monomer of which the hydrophilic unit has at least a repeating unit structure of an acrylamide structure represented by the following general formula (1): I. Pigment Yellow 3, 74, 93, 95, 109, 120, 128, 138, 151, 175, 183, 184; I. Pigment Red 12, 122, 184, 202; I. Pigment violet 19, 32; I. Pigment Blue 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16; I. Pigment green 7; and C.I. I. By using at least one selected from the group consisting of CI Pigment Black 1, 7, 10, 31, and 32, an image having high fastness and excellent quality can be recorded stably in any case. It has been found that a pigment dispersion is provided that can be made into a possible ink.

(Wherein R ¹ , X and n are as defined above.)

  The polymer dispersant used in the present invention contains a block portion composed of a hydrophobic monomer having a hydrophobic unit having a good affinity with the pigment, so that the pigment particle in which the polymer dispersant stably encapsulates the pigment is used. Stability is improved. Furthermore, the hydrophilic unit of the polymer dispersant has a repeating unit structure of an acrylamide structure having ethylene oxide having a high affinity for water as a dispersion medium, so that the stability of the encapsulated pigment particles is further improved and the long-term performance of the ink is increased. It is thought that storage stability and discharge stability are improved. In particular, these effects can be further improved by blocking the structure of each unit. In addition, by using a pigment having a specific structure as the pigment, the affinity between the polymer dispersant and the pigment becomes the best, so that the pigment particles are more stably encapsulated, and the water content in the ink is increased. It is possible to exhibit good pigment dispersion stability even when the ink is concentrated. These effects can be further improved by providing the hydrophobic unit of the polymer dispersant with a block portion having a specific structure containing an aromatic hydrocarbon group having higher affinity with the pigment.

  In addition, since the hydrophilic unit of the polymer dispersant has an ethylene oxide structure that has a high affinity with water and water-soluble organic solvents in the pigment dispersion (ink), the ink does not remain only on the surface of the recording material, It becomes possible to penetrate into the recording material moderately together with ink penetration within a range that does not cause a decrease in image density and bleeding, and the hydrophilic unit also has an amide structure having high affinity with the recording material. Therefore, it is considered that the adhesion between the recorded image and the recording material is the best, and the fastness such as the ink fixing property and the scratch resistance of the recorded image is greatly improved. In addition, by using a pigment having a specific structure as the pigment, the affinity between the block portion made of the hydrophobic monomer of the polymer dispersant and the pigment is increased, and a more stable capsule is formed. The capsule state is maintained. In this way, the polymer dispersant firmly coats the pigment, so that it has fastness such as ink fixability and scratch resistance of the recorded image compared to the case where some of the pigment particles are exposed. Is thought to be further improved. In the case where the hydrophobic unit of the polymer dispersant has a block portion having a specific structure containing an aromatic hydrocarbon group, this effect is further improved.

  As a result of these effects, there is no decrease in color developability due to penetration of the encapsulated pigment particles into the recording material, good image fastness and fixability can be achieved, and the stability of the ink during long-term storage is improved. Even when the ink composition changes greatly, such as the ink concentration at the nozzle tip, which always occurs when used in an ink jet recording apparatus, stable dispersion of the ink without reducing the dispersion stability of the pigment particles. Is possible. Furthermore, even in the case of an ink jet apparatus having a line head that cannot frequently perform cleaning recovery operation of the ink jet nozzle, adhesion of encapsulated pigment particles to the nozzle peripheral portion can be suppressed. It is difficult to occur and good continuous printing performance can be achieved over a long period of time.

上記一般式（１）において、Ｒ¹は水素原子またはメチル基を、Ｘは水素原子または炭素数１から４のアルキル基を、好ましくは水素原子またはメチル基を表し、ｎは１から１０、好ましくは１から６である。
上記モノマー構造の繰り返し単位数としては、１０から２００、好ましくは２０から１５０、より好ましくは２０から１００であると、カプセル化顔料粒子の分散安定性と被記録材上でのインクの定着性がより向上するため望ましい。 Hereinafter, the constituent materials of the pigment dispersion of the present invention will be described in more detail.
(Polymer dispersant)
The polymer dispersant used in the present invention is composed of at least a hydrophobic unit and a hydrophilic unit, the hydrophobic unit has a block portion composed of at least one hydrophobic monomer, and the hydrophilic unit is at least It is a copolymer having a repeating unit structure of acrylamide structure represented by the following general formula (1).

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, X represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, preferably a hydrogen atom or a methyl group, and n is 1 to 10, preferably Is 1-6.
When the number of repeating units of the monomer structure is 10 to 200, preferably 20 to 150, more preferably 20 to 100, the dispersion stability of the encapsulated pigment particles and the fixability of the ink on the recording material are improved. Desirable for further improvement.

  Examples of the monomer used to form the structure of the general formula (1) include N- (2-hydroxyethyl) acrylamide, N- (2- (2-hydroxyethoxy) ethyl) acrylamide, and N- (2 -(2- (2-hydroxyethoxy) ethoxy) ethyl) methacrylamide, N- (methoxyethyl) acrylamide, N- (2- (2-ethoxyethoxy) ethyl) acrylamide, N- (2- (2- (2 -Butoxyethoxy) ethoxy) ethyl) methacrylamide and N- (2- (2- (2- (2- (2- (2-Methoxyethoxy) ethoxy) ethoxy) ethoxy) ethoxy) ethyl) methacrylamide) and the like. . These can be used alone or in combination of two or more.

  The hydrophobic unit of the polymer dispersant need only have a block portion composed of at least one kind of hydrophobic monomer, and even when two or more kinds of hydrophobic monomers are contained, only these hydrophobic monomers are contained. Can be used in a random state or in a block state, but preferably each hydrophobic monomer is constituted in a block state. This is desirable because stable encapsulated pigment particles can be formed. As the repeating unit of the hydrophobic monomer in the block portion composed of the hydrophobic monomer, when composed of two or more kinds of hydrophobic monomers, the total number of the repeating units of these hydrophobic monomers is 10 to 200, preferably A thickness of 20 to 150, more preferably 20 to 100 is desirable because the affinity between the polymer dispersant and the pigment is improved. Further, the ratio of the number of repeating units (a) of the hydrophobic monomer to the number of repeating units (b) of the monomer structure of the above general formula (1) is such that a / b is 0.1 to 10, preferably 0.5 to 5. Within the range, it is desirable because both the dispersion stability of the encapsulated pigment particles and the fixability of the ink on the recording material are improved.

上記一般式（２）におけるＲ²は水素原子またはメチル基であるのが好ましく、Ｙは−Ｒ³、−ＯＲ³または−ＣＯＯＲ³であるのが好ましい。ここでＲ³は炭素数１から１８のアルキル基であるのが好ましい。このようなモノマーとしては、例えば、１−メチル−４−ビニルベンゼン、１−エチル−４−（プロペン−２−イル）ベンゼン、１−ブチル−４−（プロペン−２−イル）ベンゼン、１−ドデシル−４−（プロペン−２−イル）ベンゼン、４−メトキシ−ビニルベンゼン、４−ブトキシ−ビニルベンゼン、メチル−４−ビニルベンゾエート、ブチル−４−ビニルベンゾエート、ドデシル−４−ビニルベンゾエート、ヘキサデシル−４−ビニルベンゾエート、オクタデシル−４−ビニルベンゾエートなどが挙げられる。これらは単独でも２種以上を組み合わせて使用することも可能である。 As the hydrophobic monomer, any monomer can be used as long as it is copolymerizable with a monomer having an acrylamide structure constituting the hydrophilic unit, and a vinyl monomer having a hydrophobic substituent is preferred. Among them, a monomer constituting the repeating unit structure represented by the following general formula (2) is preferable because the affinity between the polymer dispersant and the pigment is further improved and stable encapsulated pigment particles can be formed.

R ² in the general formula (2) is preferably a hydrogen atom or a methyl group, and Y is preferably —R ³ , —OR ³ or —COOR ³ . Here, R ³ is preferably an alkyl group having 1 to 18 carbon atoms. Examples of such monomers include 1-methyl-4-vinylbenzene, 1-ethyl-4- (propen-2-yl) benzene, 1-butyl-4- (propen-2-yl) benzene, 1- Dodecyl-4- (propen-2-yl) benzene, 4-methoxy-vinylbenzene, 4-butoxy-vinylbenzene, methyl-4-vinylbenzoate, butyl-4-vinylbenzoate, dodecyl-4-vinylbenzoate, hexadecyl- 4-vinyl benzoate, octadecyl-4-vinyl benzoate, etc. are mentioned. These can be used alone or in combination of two or more.

  Moreover, as a hydrophilic unit of the polymer dispersant, if it contains a monomer unit having the structure of the general formula (1), it has both a monomer structure having other hydrophobic substituents and hydrophilic substituents. However, a monomer structure having a hydrophilic substituent is preferable because the dispersion stability of the pigment is further improved. As such a monomer having an anionic hydrophilic group as a hydrophilic substituent, it is preferable because the dispersion stability of the pigment is further improved. For example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, Examples thereof include fumaric acid, styrene sulfonic acid, styrene carboxylic acid, mono- (2-acryloyloxy-1-methyl-ethyl) phthalate, and among them, acrylic acid and methacrylic acid are preferable from the viewpoint of polymerizability. These can be used individually or in mixture of 2 or more types. At this time, if the hydrophilic unit is composed of a block portion having a repeating unit structure of the general formula (1) and a block portion of a segment having an anionic hydrophilic group, encapsulation on a recording material is performed. It is desirable because the fixability of the pigment particles becomes even better. In particular, the polymer dispersant is in the order of a block part composed of a repeating unit structure of the general formula (2), a block part composed of a repeating unit structure of the general formula (1), and a block part of a segment having an anionic hydrophilic group. If it is at least constituted, the dispersion stability of the encapsulated pigment particles and the fixing property of the ink on the recording material are the best and more desirable.

  In the polymer dispersant used in the present invention, the above monomers can be obtained by a conventional polymerization method such as radical polymerization or anionic polymerization, and particularly, a living radical polymerization method is preferably used. By using the living radical polymerization method, it is possible to produce a copolymer or a block copolymer having exactly the same length (molecular weight). These polymer dispersants preferably have a weight average molecular weight in the range of 3,000 to 50,000, more preferably 5,000 to 30,000. The obtained polymer dispersant can be identified by qualitative and quantitative determination of functional groups by NMR or IR, or analysis by various chromatography.

  When the polymer dispersant has an anionic hydrophilic group, the acid value of the polymer dispersant is preferably 10 to 150 mgKOH / g, more preferably 30 to 100 mgKOH / g, and the fixability and color development of the printed image. Desirable in terms of sex. Further, the anionic hydrophilic group of the polymer dispersant needs to be neutralized with an alkali, but it can be used even if it contains an unneutralized anionic hydrophilic group. When it is 50 to 100 mol%, more preferably 80 to 100 mol%, it is desirable because the ink discharge property is hardly lowered. The method of neutralizing an anionic hydrophilic group is a method in which a vinyl monomer containing an anionic hydrophilic group is first neutralized with an alkali and then polymerized, or after a vinyl monomer containing an anionic hydrophilic group is polymerized and then after an alkali. Any method of neutralizing from the above can be used, but a method of neutralizing later from the polymerization side of the monomer is preferred. Examples of the alkali used for the neutralization include ions of alkali metals such as lithium ion, sodium ion and potassium ion, and amines such as ammonia, monoethanolamine and triethanolamine. This is preferable because the dischargeability of the ink is further improved. Specific examples include potassium hydroxide, sodium hydroxide, lithium hydroxide, potassium carbonate, sodium carbonate, lithium carbonate and the like. In addition, the acid value of the polymer dispersant in this invention shows the value measured according to the acid value measuring method as described in Japanese Industrial Standard JIS-K0070.

  The content of the polymer dispersant in the pigment dispersion is preferably in the range of 0.5 to 30% by mass, more preferably 1.0 to 20% by mass of the total mass of the pigment dispersion. The amount is preferably in the range of 0.1 to 15% by weight, more preferably 0.5 to 10% by weight of the total ink.

(Pigment)
The pigment used in the present invention is C.I. I. Pigment Yellow 3, 74, 93, 95, 109, 120, 128, 138, 151, 175, 183, 184; I. Pigment Red 12, 122, 184, 202; I. Pigment violet 19, 32; I. Pigment Blue 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16; I. Pigment green 7; and C.I. I. At least one selected from the group consisting of CI Pigment Black 1, 7, 10, 31, 32 is used. These pigments can be used alone or in combination of two or more. In addition to these pigments, other pigments can be added within a range of 5% or less with respect to the total mass of all pigments.

  The content of these pigments in the pigment dispersion is preferably 0.5 to 30% by mass, more preferably 1.0 to 20% by mass with respect to the total mass of the pigment dispersion, and the content in the ink Is preferably from 0.1 to 15 mass%, more preferably from 0.5 to 10 mass%, based on the total mass of the ink. When the amount of the pigment in the ink is less than 0.1% by mass, it may be difficult to obtain a sufficient image density. When the amount of the pigment exceeds 15% by mass, the ejection stability is reduced due to clogging in the nozzle. There is a case. Further, the content ratio of the pigment and the polymer dispersant is preferably 10: 1 to 1: 3, more preferably 5: 1 to 1: 2 in terms of solid content, and the fixability of the printed image can be improved. It is desirable from the viewpoints of robustness, ink ejection stability and storage stability.

  Moreover, the average particle diameter of the encapsulated pigment particles that these pigments form with the polymer dispersant in the pigment dispersion is preferably in the range of 50 nm to 200 nm, more preferably 50 nm to 150 nm. If the average particle diameter of the encapsulated pigment particles is within this range, the ink ejection stability is further improved, and the color development of the printed image is also improved. The particle diameter in the present invention is a value measured using a laser light scattering method.

Moreover, the water which is a dispersion medium of the pigment dispersion liquid of the present invention is not particularly limited, and is tap water, deionized water, ion exchange water, pure water or the like, and deionized water is preferable. The amount of water used is such a ratio that the pigment concentration falls within the above range.
The above is the material mainly constituting the pigment dispersion of the present invention, but in addition to these, it is preferable to use a water-soluble organic solvent. As the water-soluble organic solvent used in the pigment dispersion of the present invention, any water-soluble organic solvent can be used, and it can be used as a mixed solvent of two or more water-soluble organic solvents.

  Specific examples of preferred water-soluble organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and other lower alcohols; ethylene glycol, diethylene glycol, Triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, thiodiglycol, 1,4-cyclohexanediol Diols such as: Triols such as 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,5-pentanetriol; Trimethylolpropane, trimethyl Hindered alcohols such as roll ethane, neopentyl glycol, pentaerythritol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono Glycol ethers such as butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether; glycerin, dimethyl sulfoxide, glycerin monoallyl ether, polyethylene glycol, N-methyl- 2- Loridone, 2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, sulfolane, β-dihydroxyethylurea, urea, acetonylacetone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, acetone, diacetone alcohol, etc. It is.

  In addition to the above components, various additives such as surfactants, pH adjusters, antioxidants, and antifungal agents may be added.

  In addition, it is preferable to add calcium ions and / or magnesium ions to the pigment dispersion because the long-term storage stability of the pigment dispersion and the ejection stability with ink are improved. This is because the interaction between polymer dispersants is improved by the effect of cross-linking of calcium and magnesium ions with a bivalent positive charge on the polymer dispersant, and the capsule shape of the encapsulated pigment particles is stabilized. Is done. For this reason, even when the capsule shape tends to become unstable, such as when the ink is heated, the entire capsule is maintained in a uniform shape. This is presumably because the state is maintained uniformly and aggregation and association of capsules due to electrostatic factors are greatly reduced.

The content of calcium ions and magnesium ions in the pigment dispersion is such that the total amount of calcium ions and magnesium ions (A) is preferably in a mass ratio with respect to the polymer dispersant (B), and A: B is 1: A range of 100,000 or more and 1: 100 or less, more preferably A: B is a range of 1: 20000 or more and 1: 200 or less is preferable because the storage stability of the pigment dispersion is further improved. If the content of calcium ions and magnesium ions is less than the above range, the effect of improving the storage stability of the pigment dispersion may be reduced, and if the content is more than the above range, nozzle clogging may be likely to occur. Specific examples of preferable calcium ions and magnesium ions to be added to the pigment dispersion include calcium chloride, magnesium chloride, calcium nitrate, magnesium nitrate, calcium sulfate, magnesium sulfate, calcium hydroxide, magnesium hydroxide, calcium oxide and Examples thereof include magnesium oxide.
The pigment dispersion of the present invention can be obtained by dispersing a pigment in water using the above-described polymer dispersant by a conventionally known pigment dispersion technique. As a preferable production method, the polymer dispersant is preferably dissolved in an organic solvent such as methylethylkenton, acetone, methanol, ethanol, and tetrahydrofuran to form a solution (concentration 1 to 30% by mass). Is sufficiently kneaded at the above solid content ratio to disperse the pigment, and the pigment particles are coated with the polymer dispersant, and then the solvent is distilled off. The resulting mixture is shaped into flakes, sheets, powders, etc., and this is added to an appropriate amount of water containing an appropriate amount of an alkaline substance and stirred to obtain the pigment dispersion of the present invention.

  The inkjet recording ink of the present invention is an ink obtained by mixing the pigment dispersion and at least a water-soluble organic solvent. As the water-soluble organic solvent used in the ink jet recording ink of the present invention, those described in the section of the pigment dispersion can be preferably used. Among these, it is preferable to use a water-soluble organic solvent having a boiling point of 120 ° C. or more because ink concentration at the nozzle tip is suppressed. The proportion of these water-soluble organic solvents in the ink is preferably 5 to 50% by mass, more preferably 10 to 30% by mass, based on the total mass of the ink.

  In addition, when mixing the pigment dispersion and the water-soluble organic solvent, various additives such as water, a surfactant, a pH adjuster, an antioxidant, and an antifungal agent are added as necessary. Also good.

  Furthermore, when the pH of the ink is adjusted preferably in the range of 8.0 to 10.0, more preferably in the range of 8.4 to 9.8, the long-term storage stability of the ink is improved, and long-term storage is achieved. This is preferable because a subsequent drop in ink discharge is suppressed. Examples of the pH adjuster include organic amines such as triethanolamine, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, and organic acids.

  A feature of the ink jet recording method of the present invention is that the ink of the present invention is used in an ink jet recording method performed by applying energy to the ink and causing the ink to fly. As the energy, thermal energy or mechanical energy can be used, but it is preferable to use thermal energy.

  In the ink jet recording method of the present invention, the recording material is not limited, but so-called ink jet exclusive paper, postcards and business card paper, label paper, cardboard paper, ink jet film and various copy papers are preferably used. As the recording material having a coating layer, a recording material having a coating layer for receiving ink on at least one surface containing at least a hydrophilic polymer and / or an inorganic porous material is desirable.

  Examples of the ink jet recording apparatus that performs recording using the ink of the present invention include a general household printer mainly using A4 size paper, a printer for printing business cards and cards, or a large business printer. However, an example of a suitable inkjet recording apparatus will be described below.

(Inkjet recording device using thermal energy)
FIG. 1 is a diagram illustrating an example of an ink cartridge 100 that stores ink supplied to a head via an ink supply tube 104. Reference numeral 101 denotes an ink bag containing ink for supply, and a stopper 102 made of chlorinated butyl rubber is provided at the tip thereof. By inserting the needle 103 into the stopper 102, the ink in the ink bag 101 can be supplied to the recording head (303 to 306). An ink absorber that receives waste ink may be provided in the ink cartridge. The ink jet recording apparatus used in the present invention is not limited to the one in which the recording head and the ink cartridge are separated as described above, and an apparatus in which they are integrated is also preferably used.

  FIG. 2 is a schematic diagram for explaining the structure of the ink jet recording head used in this embodiment. Each nozzle 202 is provided with a corresponding heating element 204 (heater), which is heated by applying a predetermined driving pulse from the recording head driving circuit to the heater 204 to generate air bubbles. Ink droplets are discharged from the discharge port 202. The heater 204 is formed on the silicon substrate 206 by the same method as in the semiconductor manufacturing process. Reference numeral 203 denotes a nozzle partition that constitutes each nozzle 202, 205 denotes a common liquid chamber for supplying ink to each nozzle 202, and 207 denotes a top plate.

  A partial perspective view of the recording apparatus according to the present embodiment is shown in FIG. The recording paper 302 of the recording apparatus 300 is supplied from, for example, a roll supply unit 301 and is continuously conveyed by a conveyance unit provided in the main body of the recording apparatus 300. The transport unit includes a transport motor 312 and a transport belt 313. For recording, when the image cut-out position of the recording medium passes under the black recording head 303, the black ink starts to be ejected from the recording head. The color image is formed. In addition, the recording apparatus 300 includes a cap mechanism 311 that caps each recording head during standby, ink cartridges 307 to 310 for supplying ink to each recording head 303 to 306, and a pump for supplying and recovering ink. A unit (not shown), a control board (not shown) for controlling the entire recording apparatus, and the like are included.

  FIG. 4 is a schematic diagram of a recovery processing system in the ink jet recording apparatus used in this embodiment. When the recording head 303 is lowered from the recording head 303, a predetermined recovery operation can be executed by the ink discharge port forming surface approaching the cap 400 formed of chlorinated butyl rubber in the cap mechanism 311.

  In the recovery processing system, the ink regeneration circuit unit stores between the ink cartridge 100 in which replenished ink is stored and accommodated in a polyethylene bag, a sub tank 401 connected via a suction pump 403, and the like, and between the cap 400 and the sub tank 401. A suction pump 403 that is disposed in an ink supply path 409 formed of vinyl chloride to be connected and collects ink from the cap mechanism 311 in the sub tank 401, a filter 405 that removes dust and the like in the ink collected from the cap, and an ink supply path 408 The main components are a pressure pump 402 for supplying ink to the common liquid chambers of the recording heads 303 to 306, an ink supply path 407 for supplying ink returned from the recording head to the sub tank 401, and valves 404a to 404d. It is configured.

  When the recording heads 303 to 306 are cleaned, the recovery valve 404b is closed and the pressurizing pump 402 is operated to pressurize and supply ink from the sub tank 401 to the recording head and forcibly discharge it from the nozzle 406. As a result, bubbles, ink, dust and the like in the nozzles of the recording head are discharged. The suction pump 403 collects the ink discharged from the recording head into the cap mechanism 311 in the sub tank 401.

(Inkjet recording device using mechanical energy)
Next, as a preferable example of an ink jet recording apparatus using mechanical energy, a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed opposite to the nozzles, and the pressure An on-demand ink jet recording head that includes ink that fills the periphery of the generating element, displaces the pressure generating element by an applied voltage, and discharges a small droplet of ink from a nozzle can be exemplified. An example of the configuration of a recording head, which is the main part of the recording apparatus, is shown in FIG.

  The head includes an ink flow path 80 communicating with an ink chamber (not shown), an orifice plate 81 for ejecting ink droplets of a desired volume, a vibration plate 82 that directly applies pressure to ink, and the vibration plate 82. And a substrate 84 for indicating and fixing the orifice plate 81, the vibration plate 82, and the like.

  In FIG. 5, an ink flow path 80 is formed of a photosensitive resin or the like, an orifice plate 81 is formed with a discharge port 85 by drilling a metal such as stainless steel or nickel by electroforming or pressing, and the diaphragm 82 is The piezoelectric element 83 is formed of a dielectric material such as barium titanate or PZT. The piezoelectric element 83 is formed of a metal film such as stainless steel, nickel, or titanium and a highly elastic resin film. The recording head configured as described above applies a pulsed voltage to the piezoelectric element 83 to generate strain stress, and the energy deforms the vibration plate 82 bonded to the piezoelectric element 83, so that the inside of the ink flow path 80. An operation is performed so as to perform recording by pressurizing the ink vertically and ejecting ink droplets (not shown) from the ejection port 85 of the orifice plate 81.

Hereinafter, the present invention will be described in detail based on examples and comparative examples. The present invention is not limited to these examples. In the text, “parts” and “%” are based on mass unless otherwise specified.
In addition, for the identification of the polymer dispersant, a nuclear magnetic resonance absorption measuring apparatus (H ¹ -NMR, ECA400 manufactured by JEOL Ltd., solvent: tetrahydrofuran-d8 is used) and GPC (HLC8220 manufactured by Tosoh Corporation, column: TSK) -GEL4000HXL, TSK-GEL3000HXL, TSK-GEL2000HXL, column oven temperature 40.0 ° C).

(Preparation of polymer dispersant A)
A glass four-necked flask equipped with a reflux tube, a dropping funnel, a thermometer and a stirrer was purged with nitrogen, and then charged with 100 parts of dimethylformamide and 0.5 part of pentamethyldiethylenetriamine, and then as a hydrophobic monomer of the hydrophobic unit 36 mmol of 1-methyl-4-vinylbenzene and 1 mmol of chloroethylbenzene as an initiator were added and heated with stirring. When the system temperature reached 80 ° C., 0.2 part of cuprous chloride was added to initiate polymerization, and a block part (component A) composed of a hydrophobic monomer of a hydrophobic unit was synthesized. The molecular weight is monitored in a time-sharing manner using molecular sieve column chromatography (GPC), and after the polymerization of component A is completed, N- (2 as a hydrophilic monomer that forms the acrylamide structure of the general formula (1) is then obtained. Polymerization was continued by adding 36 mmol of-(2-hydroxyethoxy) ethyl) acrylamide (component B). Similarly, the molecular weight is monitored by GPC, and after the polymerization of the B component is completed, 20 mmol of butyl methacrylate in which the carboxyl group of methacrylic acid is esterified with a butyl group as a monomer capable of forming a segment having an anionic hydrophilic group (C Ingredients) were added for synthesis. After the polymerization was stopped, the esterified carboxyl group was hydrolyzed with a sodium hydroxide / methanol solution to be converted into a carboxylic acid type to obtain an ABC triblock copolymer (polymer dispersant A). The compound was identified by NMR and GPC (Mw = 1.1 × 10 ⁴ , Mw / Mn [weight average molecular weight / number average molecular weight] = 1.2). In addition, when the acid value of the obtained polymer dispersing agent was measured, it was 80 mgKOH / g.

(Preparation of polymer dispersants B to G)
Polymer dispersants B to G shown in Table 1 were prepared by changing the monomer types and addition amounts of the hydrophobic unit and the hydrophilic unit in the same manner as in the polymer dispersant A. In the polymer dispersants E and F, the B monomer and the C monomer were mixed and added, and the polymer dispersant G was prepared by synthesis without adding the C monomer.

[Example 1]
(Preparation of pigment dispersion 1)
A methyl ethyl ketone solution of the polymer dispersant A and commercially available pigments such as C.I. I. Pigment Black 7 was charged into a kneader having a twin screw and kneaded until uniform, and then the solvent was distilled off under reduced pressure while maintaining the internal temperature at 80 ° C. This kneaded product is made into a sheet using two rolls, and a predetermined amount of ion-exchanged water and sodium hydroxide as a neutralizing agent are added in an amount corresponding to 1 equivalent of the anionic group of the polymer dispersant. A 2% calcium chloride aqueous solution was added and stirred to obtain a pigment dispersion 1 having a pigment concentration of 15% and a polymer dispersant concentration of 10%. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 2]
(Preparation of pigment dispersion 2)
The polymer dispersant of Example 1 was changed to the polymer dispersant B, and the pigment was changed to C.I. I. Pigment black 1 was obtained in the same manner as in Example 1 except that the pigment concentration was 20% and the polymer dispersant concentration was 4%. When the mass ratio of calcium ions to the polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 20000.

[Example 3]
(Preparation of pigment dispersion 3)
The polymer dispersant of Example 1 was changed to the polymer dispersant C, and the pigment was changed to C.I. I. Pigment black 10 was obtained in the same manner as in Example 1 except that the pigment concentration was 1% and the polymer dispersant concentration was 2%. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 200.

[Example 4]
(Preparation of pigment dispersion 4)
The polymer dispersant of Example 1 was changed to the polymer dispersant D, and the pigment was changed to C.I. I. Pigment black 31 was replaced with calcium chloride, and in the same manner as in Example 1, pigment dispersion 4 having a pigment concentration of 30% and a polymer dispersant concentration of 3% was obtained. When the mass ratio of magnesium ion and polymer dispersant in the obtained pigment dispersion was measured, it was magnesium ion: polymer dispersant = 1: 100000.

[Example 5]
(Preparation of pigment dispersion 5)
The polymer dispersant of Example 1 was used as the polymer dispersant E, and the pigment as C.I. I. In Pigment Black 32, calcium chloride was changed to a mixture of calcium chloride and magnesium chloride (molar ratio 1: 1), and in the same manner as in Example 1, the pigment concentration was 0.5% and the polymer dispersant concentration was 1.5%. A pigment dispersion 5 was obtained. When the mass ratio of the total amount of calcium ions and magnesium ions and the polymer dispersant in the obtained pigment dispersion was measured, the total amount of calcium ions and magnesium ions: polymer dispersant = 1: 100.

[Comparative Example 1]
(Preparation of pigment dispersion 6)
C. used in Example 1 I. Pigment Black 7 was used, and a styrene-2-hydroxypropyl acrylate-maleic acid random copolymer (number average molecular weight 10,000, acid value 160 mgKOH / g, number of styrene segments / 2 segments of 2-hydroxypropyl acrylate) as a polymer dispersant A pigment dispersion 6 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 1 except that the number = 11) was used.

[Comparative Example 2]
(Preparation of pigment dispersion 7)
C. used in Example 1 I. Pigment Black 7 and octadecyl methacrylate-N, N-dimethylacrylamide block copolymer as a polymer dispersant (number average molecular weight 17000, number of segments of octadecyl methacrylate / number of segments of N, N-dimethylacrylamide = 0.07) ) Was used in the same manner as in Example 1 to obtain a pigment dispersion 7 having a pigment concentration of 15% and a polymer dispersant concentration of 10%.

[Comparative Example 3]
(Preparation of pigment dispersion 8)
C. used in Example 1 I. Pigment Dispersion 8 having a pigment concentration of 15% and a polymer dispersant concentration of 10%, as in Example 1, except that Pigment Black 7 was used and polyoxyethylene hexadecyl ether (HLB 12.9) was used as the dispersant. Got.

(Evaluation 1)
Using the pigment dispersions of Examples 1 to 5 and Comparative Examples 1 to 3, the following components were mixed and sufficiently stirred to prepare inks.
・ Pigment dispersion 30.0 parts ・ Triethylene glycol 10.0 parts ・ Tripropylene glycol 10.0 parts ・ Ion-exchanged water 50.0 parts

  Dispersion stability of pigment dispersions of Examples 1 to 5 and Comparative Examples 1 to 3, ejection stability of inks using the pigment dispersions of Examples 1 to 5 and Comparative Examples 1 to 3, and images of printed images Tests for quality, robustness and storage stability were performed. As for image quality, robustness, and ejection stability, an inkjet recording apparatus P-660CII having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to the recording signal to each ink. Each was mounted on Canon Finetech), printed on plain paper GF-500 (manufactured by Canon), and evaluated. As a result, as described in Table 2, the pigment dispersions of all the examples had better dispersion stability than the pigment dispersions of the comparative examples. In addition, the inks of the examples also had better storage stability and ejection stability than the comparative inks, and the image quality and fastness were good.

◎：粒子径増加率（％）が５％未満である。
○：粒子径増加率（％）が５％以上１０％未満である。
△：粒子径増加率（％）が１０％以上３０％未満である。
×：粒子径増加率（％）が３０％以上である。 * 1: Dispersion stability After each pigment dispersion was stored in a sealed state at 80 ° C for 2 weeks, the particle size before and after the test was measured, and the rate of increase in particle size (%) was calculated using the following formula as a measure of dispersion stability. . A dynamic light scattering method (trade name: Laser particle size analysis system FPAR-1000; manufactured by Otsuka Electronics Co., Ltd.) was used for the measurement of the particle size. The evaluation criteria were as follows.

A: The particle diameter increase rate (%) is less than 5%.
○: The particle diameter increase rate (%) is 5% or more and less than 10%.
Δ: Particle diameter increase rate (%) is 10% or more and less than 30%.
X: The particle diameter increase rate (%) is 30% or more.

* 2: Intermittent ejection stability After storing each ink at 70 ° C for 2 weeks, in a 10% humidity environment at 15 ° C, print a 100% solid image, pause for 3 minutes, and then reprint the 100% solid image again. The printed image was evaluated according to the following evaluation criteria.
A: There are no white stripes and printing is normal.
○: Slight white streaks are observed at the beginning of printing.
Δ: White streaks are observed in the entire image.
X: An image is hardly printed.

* 3: Continuous discharge stability 1000 postcard-size gradation patterns were continuously printed, and the deviation and discharge failure characteristics of the 1000th image were evaluated according to the following criteria.
A: Printed normally without twisting or non-discharge.
○: No discharge occurred, but some irregularities were observed.
Δ: Some undischarge occurred, and a twist was observed in the entire image.
X: Many undischarge occurred, and twist is seen in the whole image.

* 4: Image quality An image was printed with each ink stored at 70 ° C. for 2 weeks, and the image was evaluated according to the following evaluation criteria.
(Double-circle): There is no blur of an image and saturation is high.
○: There is no blur of the image, but the saturation is slightly low.
Δ: Some blurring of the image is observed.
X: Image blurring is large and saturation is low.

* 5: Fastness 100% solid images are printed with each ink stored at 70 ° C for 2 weeks. After 1 minute, the printed part is rubbed with sylbon paper under a load of 2 x 10 ⁴ N / m ² Evaluation was performed according to the following evaluation criteria.
(Double-circle): There is no rubbing of an image and there is no adhesion to a silver paper.
○: There is no image rubbing, but adhesion to the Sylbon paper is observed.
Δ: Some image rubbing is observed.
X: There is much rubbing of an image.

◎：粒子径増加率（％）が５％未満である。
○：粒子径増加率（％）が５％以上１０％未満である。
△：粒子径増加率（％）が１０％以上３０％未満である。
×：粒子径増加率（％）が３０％以上である。 * 6: Storage stability After each ink was stored in a sealed state at 70 ° C. for 2 weeks, the particle size before and after the test was measured, and the increase rate (%) of the particle size was obtained by the following formula and used as a measure of storage stability. A dynamic light scattering method (trade name: Laser particle size analysis system FPAR-1000; manufactured by Otsuka Electronics Co., Ltd.) was used for the measurement of the particle size. The evaluation criteria were as follows.

A: The particle diameter increase rate (%) is less than 5%.
○: The particle diameter increase rate (%) is 5% or more and less than 10%.
Δ: Particle diameter increase rate (%) is 10% or more and less than 30%.
X: The particle diameter increase rate (%) is 30% or more.

[Example 6]
(Preparation of pigment dispersion 9)
A methyl ethyl ketone solution of the polymer dispersant A and commercially available pigments such as C.I. I. Pigment Yellow 128 was charged into a kneader having a twin screw and kneaded until uniform, and then the solvent was distilled off under reduced pressure while maintaining the internal temperature at 80 ° C. This kneaded product is made into a sheet using two rolls, and a predetermined amount of ion-exchange water and potassium hydroxide as a neutralizing agent are added in an amount corresponding to 1 equivalent of the anionic group of the polymer dispersant. A 2% calcium chloride aqueous solution was added and stirred to obtain a pigment dispersion 9 having a pigment concentration of 15% and a polymer dispersant concentration of 10%. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 7]
(Preparation of pigment dispersion 10)
The pigment of Example 6 is C.I. I. Pigment Yellow 3 was used, and Pigment Dispersion Liquid 10 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 8]
(Preparation of pigment dispersion 11)
The polymer dispersant of Example 6 was changed to the polymer dispersant B, and the pigment was changed to C.I. I. Pigment Yellow 74 was used, and Pigment Dispersion 11 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 9]
(Preparation of pigment dispersion 12)
The polymer dispersant of Example 6 was changed to the polymer dispersant B, and the pigment was changed to C.I. I. Pigment Yellow 93 was used, and Pigment Dispersion Liquid 12 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 10]
(Preparation of pigment dispersion 13)
The polymer dispersant of Example 6 was changed to the polymer dispersant C, and the pigment was changed to C.I. I. Pigment Yellow 95 was used, and Pigment Dispersion 13 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 11]
(Preparation of pigment dispersion 14)
The polymer dispersant of Example 6 was changed to the polymer dispersant C, and the pigment was changed to C.I. I. Pigment Yellow 109 was used, and Pigment Dispersion Liquid 14 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 12]
(Preparation of pigment dispersion 15)
The polymer dispersant of Example 6 was changed to the polymer dispersant D, and the pigment was changed to C.I. I. Pigment yellow 120 was used, and pigment dispersion 15 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 13]
(Preparation of pigment dispersion 16)
The polymer dispersant of Example 6 was changed to the polymer dispersant D, and the pigment was changed to C.I. I. Pigment Yellow 138 was used, and Pigment Dispersion Liquid 16 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 14]
(Preparation of pigment dispersion 17)
The polymer dispersant of Example 6 was used as the polymer dispersant E, and the pigment as C.I. I. Pigment Yellow 151 was used, and in the same manner as Example 6, a pigment dispersion 17 having a pigment concentration of 20% and a polymer dispersant concentration of 4% was obtained. When the mass ratio of calcium ions to the polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 20000.

[Example 15]
(Preparation of pigment dispersion 18)
The polymer dispersant of Example 6 was used as the polymer dispersant E, and the pigment as C.I. I. Pigment Yellow 175 was used, and in the same manner as Example 6, a pigment dispersion 18 having a pigment concentration of 1% and a polymer dispersant concentration of 2% was obtained. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 200.

[Example 16]
(Preparation of pigment dispersion 19)
The polymer dispersant of Example 6 was changed to the polymer dispersant F, and the pigment was changed to C.I. I. In Pigment Yellow 183, calcium chloride was changed to magnesium chloride, and a pigment dispersion 19 having a pigment concentration of 30% and a polymer dispersant concentration of 3% was obtained in the same manner as in Example 6. When the mass ratio of magnesium ion and polymer dispersant in the obtained pigment dispersion was measured, it was magnesium ion: polymer dispersant = 1: 100000.

[Example 17]
(Preparation of pigment dispersion 20)
The polymer dispersant of Example 6 was used as the polymer dispersant G, and the pigment as C.I. I. In Pigment Yellow 184, calcium chloride was changed to a mixture of calcium chloride and magnesium chloride (molar ratio 1: 1), and in the same manner as in Example 6, the pigment concentration was 0.5% and the polymer dispersant concentration was 1.5%. A pigment dispersion 20 was obtained. When the mass ratio of the total amount of calcium ions and magnesium ions and the polymer dispersant in the obtained pigment dispersion was measured, the total amount of calcium ions and magnesium ions: polymer dispersant = 1: 100.

[Comparative Example 4]
(Preparation of pigment dispersion 21)
C. used in Example 6 I. Pigment Yellow 128 and a styrene-2-hydroxypropyl acrylate-maleic acid random copolymer as a polymer dispersant (number average molecular weight 10,000, acid value 160 mgKOH / g, number of styrene segments / 2-hydroxypropyl acrylate segments A pigment dispersion 21 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 6 except that the number = 11) was used.

[Comparative Example 5]
(Preparation of pigment dispersion 22)
C. used in Example 6 I. Pigment Yellow 128 and octadecyl methacrylate-N, N-dimethylacrylamide block copolymer as a polymer dispersant (number average molecular weight 17000, number of segments of octadecyl methacrylate / number of segments of N, N-dimethylacrylamide = 0.07) ) Was used in the same manner as in Example 6 to obtain a pigment dispersion 22 having a pigment concentration of 15% and a polymer dispersant concentration of 10%.

[Comparative Example 6]
(Preparation of pigment dispersion 23)
C. used in Example 6 I. Pigment Dispersion Liquid 23 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was used in the same manner as in Example 6 except that CI Pigment Yellow 128 was used and polyoxyethylene hexadecyl ether (HLB 12.9) was used as the dispersant. Got.

(Evaluation 2)
Using the pigment dispersions of Examples 6 to 17 and Comparative Examples 4 to 6, the following components were mixed and sufficiently stirred to prepare inks.
・ Pigment dispersion 30.0 parts ・ Glycerin 10.0 parts ・ Ethylene glycol 20.0 parts ・ Ion-exchanged water 40.0 parts

  Dispersion stability of the pigment dispersions of Examples 6 to 17 and Comparative Examples 4 to 6, and ejection stability of the inks using the pigment dispersions of Examples 6 to 17 and Comparative Examples 4 to 6 Tests for quality, robustness and storage stability were performed. As for image quality, robustness, and ejection stability, an inkjet recording apparatus P-660CII having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to the recording signal to each ink. Each was mounted on Canon Finetech), printed on plain paper GF-500 (manufactured by Canon), and evaluated. As a result, as described in Table 3, the pigment dispersions of all the examples had better dispersion stability than the pigment dispersions of the comparative examples. In addition, the inks of the examples also had better storage stability and ejection stability than the comparative inks, and the image quality and fastness were good.

[Example 18]
(Preparation of pigment dispersion 24)
A methyl ethyl ketone solution of the polymer dispersant A and commercially available pigments such as C.I. I. Pigment Red 122 was charged into a kneader having a twin screw and kneaded until uniform, and then the solvent was distilled off under reduced pressure while maintaining the internal temperature at 80 ° C. This kneaded product is made into a sheet using two rolls, and a predetermined amount of ion-exchanged water and sodium hydroxide as a neutralizing agent are added in an amount corresponding to 1 equivalent of the anionic group of the polymer dispersant. A 2% calcium chloride aqueous solution was added and stirred to obtain a pigment dispersion 24 having a pigment concentration of 15% and a polymer dispersant concentration of 10%. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 19]
(Preparation of pigment dispersion 25)
The polymer dispersant of Example 18 was changed to polymer dispersant B, and the pigment was changed to C.I. I. Pigment Red 12 was used, and a pigment dispersion 25 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 18. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 20]
(Preparation of pigment dispersion liquid 26)
The polymer dispersant of Example 18 was changed to Polymer Dispersant C, and the pigment was changed to C.I. I. Pigment Red 184 was used, and Pigment Dispersion Liquid 26 having a pigment concentration of 20% and a polymer dispersant concentration of 4% was obtained in the same manner as Example 18. When the mass ratio of calcium ions to the polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 20000.

[Example 21]
(Preparation of pigment dispersion liquid 27)
The polymer dispersant of Example 18 was changed to the polymer dispersant D, and the pigment was changed to C.I. I. Pigment Red 202 was used, and Pigment Dispersion Liquid 27 having a pigment concentration of 1% and a polymer dispersant concentration of 2% was obtained in the same manner as Example 18. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 200.

[Example 22]
(Preparation of pigment dispersion 28)
The polymer dispersant of Example 18 was used as the polymer dispersant E, and the pigment as C.I. I. In Pigment Violet 19, calcium chloride was changed to magnesium chloride, and a pigment dispersion 28 having a pigment concentration of 30% and a polymer dispersant concentration of 3% was obtained in the same manner as in Example 18. When the mass ratio of magnesium ion and polymer dispersant in the obtained pigment dispersion was measured, it was magnesium ion: polymer dispersant = 1: 100000.

[Example 23]
(Preparation of pigment dispersion 29)
The polymer dispersant of Example 18 was changed to the polymer dispersant F, and the pigment was changed to C.I. I. In Pigment Violet 32, calcium chloride was changed to a mixture of calcium chloride and magnesium chloride (molar ratio 1: 1), and in the same manner as in Example 18, the pigment concentration was 0.5% and the polymer dispersant concentration was 1.5%. A pigment dispersion 29 was obtained. When the mass ratio of the total amount of calcium ions and magnesium ions and the polymer dispersant in the obtained pigment dispersion was measured, the total amount of calcium ions and magnesium ions: polymer dispersant = 1: 100.

[Comparative Example 7]
(Preparation of pigment dispersion 30)
C. used in Example 18 I. Pigment Red 122 is used, and a styrene-2-hydroxypropyl acrylate-maleic acid random copolymer (number average molecular weight 10,000, acid value 160 mgKOH / g, number of styrene segments / 2-hydroxypropyl acrylate segments as a polymer dispersant A pigment dispersion 30 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 18 except that the number = 11) was used.

[Comparative Example 8]
(Preparation of pigment dispersion 31)
C. used in Example 18 I. Pigment Red 122 and octadecyl methacrylate-N, N-dimethylacrylamide block copolymer as a polymer dispersant (number average molecular weight 17000, number of segments of octadecyl methacrylate / number of segments of N, N-dimethylacrylamide = 0.07) The pigment dispersion 31 having a pigment concentration of 15% and a polymer dispersing agent concentration of 10% was obtained in the same manner as in Example 18 except that (1) was used.

[Comparative Example 9]
(Preparation of pigment dispersion 32)
C. used in Example 18 I. Pigment dispersion 32 having a pigment concentration of 15% and a polymer dispersant concentration of 10% in the same manner as in Example 18 except that Pigment Red 122 was used and polyoxyethylene hexadecyl ether (HLB 12.9) was used as the dispersant. Got.

(Evaluation 3)
Using the pigment dispersions of Examples 18 to 23 and Comparative Examples 7 to 9, the following components were mixed and sufficiently stirred to prepare inks.
-Pigment dispersion 40.0 parts-Diethylene glycol 10.0 parts-1,2-butanediol 5.0 parts-Polyethylene glycol 600 5.0 parts-2-pyrrolidone 5.0 parts-Ion-exchanged water 35.0 parts

  Dispersion stability of the pigment dispersions of Examples 18 to 23 and Comparative Examples 7 to 9, and ejection stability of the inks using the pigment dispersions of Examples 18 to 23 and Comparative Examples 7 to 9, and images of printed images Tests for quality, robustness and storage stability were performed. As for image quality, robustness, and ejection stability, an inkjet recording apparatus P-660CII having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to the recording signal to each ink. Each was mounted on Canon Finetech), printed on plain paper GF-500 (manufactured by Canon), and evaluated. As a result, as described in Table 4, the pigment dispersions of all the examples had better dispersion stability than the pigment dispersions of the comparative examples. In addition, the inks of the examples also had better storage stability and ejection stability than the comparative inks, and the image quality and fastness were good.

[Example 24]
(Preparation of pigment dispersion liquid 33)
A methyl ethyl ketone solution of the polymer dispersant A and commercially available pigments such as C.I. I. Pigment Blue 15: 3 was charged into a kneader having a twin screw and kneaded until uniform, and then the solvent was distilled off under reduced pressure while maintaining the internal temperature at 80 ° C. This kneaded product is made into a sheet using two rolls, and a predetermined amount of ion-exchange water and potassium hydroxide as a neutralizing agent are added in an amount corresponding to 1 equivalent of the anionic group of the polymer dispersant. A 2% calcium nitrate aqueous solution was added and stirred to obtain a pigment dispersion 33 having a pigment concentration of 15% and a polymer dispersant concentration of 10%. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 5800.

[Example 25]
(Preparation of pigment dispersion 34)
The polymer dispersant of Example 24 was changed to the polymer dispersant B, and the pigment was changed to C.I. I. Pigment Blue 15: 1 was used, and a pigment dispersion liquid 34 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 24. When the mass ratio of calcium to the polymer dispersant in the obtained pigment dispersion was measured, it was calcium: polymer dispersant = 1: 5800.

[Example 26]
(Preparation of pigment dispersion 35)
The polymer dispersant of Example 24 was used as the polymer dispersant C, and the pigment as C.I. I. Pigment Blue 15: 2 was changed, and a pigment dispersion 35 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 24. When the mass ratio of calcium to the polymer dispersant in the obtained pigment dispersion was measured, it was calcium: polymer dispersant = 1: 5800.

[Example 27]
(Preparation of pigment dispersion 36)
The polymer dispersant of Example 24 was changed to the polymer dispersant D, and the pigment was changed to C.I. I. Pigment Blue 15: 4 was changed, and in the same manner as Example 24, a pigment dispersion 36 having a pigment concentration of 20% and a polymer dispersant concentration of 4% was obtained. When the mass ratio of calcium ions to the polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 20000.

[Example 28]
(Preparation of pigment dispersion 37)
The polymer dispersant of Example 24 was used as the polymer dispersant E, and the pigment as C.I. I. Pigment Blue 15: 6 was used, and in the same manner as in Example 24, a pigment dispersion 37 having a pigment concentration of 1% and a polymer dispersant concentration of 2% was obtained. When the mass ratio of calcium ion to polymer dispersant in the obtained pigment dispersion was measured, it was calcium ion: polymer dispersant = 1: 200.

[Example 29]
(Preparation of pigment dispersion 38)
The polymer dispersant of Example 24 was used as the polymer dispersant F, and the pigment as C.I. I. In Pigment Blue 16, calcium nitrate was changed to magnesium nitrate, and a pigment dispersion 38 having a pigment concentration of 30% and a polymer dispersant concentration of 3% was obtained in the same manner as in Example 24. When the mass ratio of magnesium ion and polymer dispersant in the obtained pigment dispersion was measured, it was magnesium ion: polymer dispersant = 1: 100000.

[Example 30]
(Preparation of pigment dispersion 39)
The polymer dispersant of Example 24 was used as the polymer dispersant G, and the pigment as C.I. I. In Pigment Green 7, the calcium nitrate was changed to a mixture of calcium chloride and magnesium nitrate (molar ratio 1: 1), and in the same manner as in Example 24, the pigment concentration was 0.5% and the polymer dispersant concentration was 1.5%. A pigment dispersion 39 was obtained. When the mass ratio of the total amount of calcium ions and magnesium ions and the polymer dispersant in the obtained pigment dispersion was measured, the total amount of calcium ions and magnesium ions: polymer dispersant = 1: 100.

[Comparative Example 10]
(Preparation of pigment dispersion 40)
C. used in Example 24 I. Pigment Blue 15: 3 was used, and a styrene-2-hydroxypropyl acrylate-maleic acid random copolymer (number average molecular weight 10,000, acid value 160 mgKOH / g, number of styrene segments / 2-hydroxypropyl acrylate) as a polymer dispersant The pigment dispersion 40 having a pigment concentration of 15% and a polymer dispersant concentration of 10% was obtained in the same manner as in Example 24 except that the number of segments was 11).

[Comparative Example 11]
(Preparation of pigment dispersion 41)
C. used in Example 24 I. Pigment Blue 15: 3 and octadecyl methacrylate-N, N-dimethylacrylamide block copolymer as a polymer dispersing agent (number average molecular weight 17000, number of segments of octadecyl methacrylate / number of segments of N, N-dimethylacrylamide = 0) 0.07) was used in the same manner as in Example 24 to obtain a pigment dispersion 41 having a pigment concentration of 15% and a polymer dispersant concentration of 10%.

[Comparative Example 12]
(Preparation of pigment dispersion 42)
C. used in Example 24 I. Pigment dispersion having a pigment concentration of 15% and a polymer dispersant concentration of 10% was the same as in Example 24 except that CI Pigment Blue 15: 3 was used and polyoxyethylene hexadecyl ether (HLB12.9) was used as the dispersant. A liquid 42 was obtained.

(Evaluation 4)
Using the pigment dispersions of Examples 24 to 30 and Comparative Examples 10 to 12, the following components were mixed and sufficiently stirred to prepare inks.
・ Pigment dispersion 50.0 parts ・ Ethylene glycol 10.0 parts ・ Trimethylolpropane 5.0 parts ・ Tetraethylene glycol 5.0 parts ・ Triethylene glycol monomethyl ether 5.0 parts ・ Ion-exchanged water 25.0 parts

  Dispersion stability of the pigment dispersions of Examples 24 to 30 and Comparative Examples 10 to 12, and ejection stability and ink images of inks using the pigment dispersions of Examples 24 to 30 and Comparative Examples 10 to 12 Tests for quality, robustness and storage stability were performed. As for image quality, robustness, and ejection stability, an inkjet recording apparatus P-660CII having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to the recording signal to each ink. Each was mounted on Canon Finetech), printed on plain paper GF-500 (manufactured by Canon), and evaluated. As a result, as described in Table 5, the pigment dispersions of all the examples had better dispersion stability than the pigment dispersions of the comparative examples. In addition, the inks of the examples also had better storage stability and ejection stability than the comparative inks, and the image quality and fastness were good.

  As described above, according to the present invention, it is possible to provide a pigment dispersion that provides an ink capable of stably recording an image having high fastness and excellent quality in any case over a long period of time. In addition, it is possible to provide an ink, an ink jet recording method, and an ink jet recording apparatus capable of recording an image having excellent fastness and quality.

It is a schematic diagram for demonstrating the structure of an ink cartridge. It is a schematic diagram for demonstrating the structure of an inkjet recording head. It is a perspective view of an inkjet recording device. It is the schematic of the recovery processing system in an inkjet recording device. It is a schematic sectional drawing which shows another structural example of an inkjet recording head.

Explanation of symbols

100: ink cartridge 101: ink bag 102: rubber stopper 103: needle 104: tube 201: base plate 202: ink nozzle (discharge port)
203: Partition 204: Nozzle heater 205: Common liquid chamber 206: Substrate 207: Top plate 300: Recording device 301: Roll supply unit 302: Recording medium (roll paper)
303: Recording head (black)
304: Recording head (cyan)
305: Recording head (magenta)
306: Recording head (yellow)
307: Ink cartridge (black)
308: Ink cartridge (cyan)
309: Ink cartridge (magenta)
310: Ink cartridge (yellow)
311: Cap mechanism 312: Conveying motor 313: Conveying belt 400: Cap 401: Sub tank 402: Pressurizing pump 403: Suction pump 404 a: Supply valve 404 b: Recovery valve 404 c: Atmospheric release valve 404 d: Recycling valve 405: Filter 406: Face (Nozzle) surface 80: ink flow path 81: orifice plate 82: diaphragm 83: piezoelectric element 84: substrate 85: discharge port

Claims (12)

Polymeric dispersants, pigments, and the predominantly pigment dispersion from the water, the pigment is encapsulated by the polymer dispersant, the polymer dispersant comprises at least a hydrophobic unit and a hydrophilic unit, The hydrophobic unit has a block part composed of at least one hydrophobic monomer, the block part is a block part composed of a repeating unit structure of the following general formula (2), and the hydrophilic unit is at least the following general formula (1) A pigment dispersion characterized by being a copolymer having a repeating unit structure of acrylamide structure.

(Wherein R ¹ represents a hydrogen atom or a methyl group, X represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is 1 to 10).

(In the formula, R ² represents a hydrogen atom or a methyl group, Y represents —R ³ , —OR ^3, or —COOR ³ , where R ³ represents an alkyl group having 1 to 18 carbon atoms.) The pigment is C.I. I. Pigment Yellow 3, 74, 93, 95, 109, 120, 128, 138, 151, 175, 183, 184; I. Pigment Red 12, 122, 184, 202; I. Pigment violet 19, 32; I. Pigment Blue 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16; I. Pigment green 7; and C.I. I. The pigment dispersion according to claim 1, wherein the pigment dispersion is at least one selected from the group consisting of CI Pigment Black 1, 7, 10, 31, 32. Wherein the hydrophilic unit is the pigment dispersion according to claim 1 or 2 has a segment having an anionic hydrophilic group. The pigment dispersion liquid according to claim 3 , wherein the hydrophilic unit has a block portion composed of the repeating unit structure of the general formula (1) and a block portion of a segment having an anionic hydrophilic group. The polymer dispersant is an order of a block part composed of the repeating unit structure of the general formula (2), a block part composed of the repeating unit structure of the general formula (1), and a block part of a segment having an anionic hydrophilic group. The pigment dispersion liquid according to claim 4 , which is at least constituted by: Contains calcium ions and / or magnesium ions, and these ions are contained in a total amount (A) in a mass ratio range of A: B from 1: 100,000 to 1: 100 with respect to the polymer dispersant (B). The pigment dispersion liquid according to claim 1, wherein the pigment dispersion liquid is used. Containing calcium ions and / or magnesium ions, these ions are contained in a total amount (A) in a mass ratio range of A: B from 1: 20000 to 1: 200 with respect to the polymer dispersant (B). The pigment dispersion liquid according to claim 1, wherein the pigment dispersion liquid is used.   An ink for ink jet recording, comprising the pigment dispersion according to any one of claims 1 to 7 and at least a water-soluble organic solvent.   An ink jet recording method according to claim 8, wherein the ink is applied to a recording material by applying energy to the ink and flying the ink to the recording material. . The inkjet recording method according to claim 9, wherein the energy is thermal energy.   An ink cartridge comprising an ink containing portion containing ink, wherein the ink is the ink for ink jet recording according to claim 8.   9. An ink jet recording apparatus comprising: an ink cartridge having an ink containing portion that contains ink; and a head portion for discharging the ink, wherein the ink is the ink for ink jet recording according to claim 8. An inkjet recording apparatus.

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