JP2016113530A - Aqueous ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous ink composition that prevents the occurrence of crystalline foreign matter derived from a pigment and also can form an image with excellent scratch resistance.SOLUTION: An aqueous ink composition comprises a pigment, a polar solvent, DNA, and water, where a ratio between a total content Σ[Cp] of the polar solvent and the content [Cd] of the DNA satisfies the relationship of 0.01≤[Cd]/Σ[Cp]≤5.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous ink composition.

  Conventionally, water-based ink compositions containing a water-soluble dye, water, a water-soluble organic solvent, a surfactant and the like are generally used as inks used for inkjet recording and the like. Water-soluble dyes have been widely used as ink colorants for reasons such as high color saturation, transparency, and high solubility in water. However, such water-soluble dyes are generally insufficient in terms of light resistance and gas resistance, and since they are water-soluble, there is also a problem with water resistance, so water-soluble dyes were used. The recorded matter recorded with the ink has a drawback that the storage stability of the recorded image is inferior.

  On the other hand, water-insoluble pigments are color materials that are excellent in light resistance, gas resistance, and water resistance. Therefore, development of water-based pigment inks that take advantage of these color material properties is underway. For example, an aqueous pigment ink in which a pigment is dispersed with a surfactant or a polymer dispersant, an aqueous pigment ink using a self-dispersing pigment having a water-dispersible functional group added to the pigment surface, or a resin in which the pigment can be dispersed in water. An aqueous pigment ink using coated fine particles has been proposed (see, for example, Patent Document 1).

JP 2006-273893 A

  However, pigments and synthetic by-products similar in structure to the pigments mixed in the pigments (hereinafter referred to as “pigment-derived components”) are insoluble in water, but slightly in aqueous ink solutions containing polar solvents. However, it became clear that it showed solubility. A part of the dissolved pigment-derived component is reprecipitated with a change in temperature environment to form a crystalline foreign matter. This foreign matter gradually clogs the head filter, causing a problem of ink ejection failure.

  Therefore, some aspects of the present invention solve at least a part of the above-described problems, thereby not only suppressing the generation of crystalline foreign substances derived from pigments, but also images having excellent abrasion resistance. An aqueous ink composition that can be formed is provided.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the water-based ink composition according to the present invention is:
Containing a pigment, a polar solvent, DNA, and water;
The ratio between the total content Σ [Cp] of the polar solvent and the content [Cd] of the DNA satisfies a relationship of 0.01 ≦ [Cd] / Σ [Cp] ≦ 5.

According to the aqueous ink composition of Application Example 1, DNA captures a pigment-derived component dissolved in an aqueous ink solution containing a polar solvent, thereby suppressing generation of crystalline foreign matters and improving storage stability. . The pigment-derived component dissolved in the aqueous ink solution is often a molecule having a planar structure such as an aromatic compound. Since DNA has a helical structure and can intercalate a molecule having a planar skeleton inside the helical structure, such a molecule can be trapped. By suppressing the generation of crystalline foreign matters derived from the pigment in the aqueous ink composition, clogging due to foreign matters in the head filter is eliminated, and ink ejection stability is improved. Further, by defining the ratio of the total polar solvent content Σ [Cp] and the DNA content [Cd] in the water-based ink composition as 0.01 ≦ [Cd] / Σ [Cp] ≦ 5, In addition to suppressing the generation of crystalline foreign matters derived from the pigment, it is possible to form an image having excellent abrasion resistance.

[Application Example 2]
In the aqueous ink composition of Application Example 1, the pigment may be a resin dispersed pigment.

[Application Example 3]
In the water-based ink composition of Application Example 1, the pigment may be a self-dispersing pigment.

  According to the aqueous ink compositions of Application Example 2 and Application Example 3, it is possible to obtain aqueous ink compositions in which pigments are uniformly and stably dispersed.

[Application Example 4]
In the aqueous ink composition of any one of Application Examples 1 to 3,
The counter cation of the phosphate group in the DNA may be at least one selected from the group consisting of hydrogen ion, lithium ion, sodium ion, potassium ion, cesium ion, ammonium ion and tetraalkylammonium ion.

  According to the water-based ink composition of Application Example 4, DNA can be rapidly dissolved in the ink aqueous solution, so that the above-described pigment-derived component can be effectively captured.

[Application Example 5]
In the aqueous ink composition of any one of Application Examples 1 to 4,
The polar solvent may include at least one selected from the group consisting of alkanediols, alkylene glycol ethers, pyrrolidones, amides, and lactones.

  According to the water-based ink composition of Application Example 5, wetting and spreading properties, penetrability, and drying properties on the recording medium can be controlled. On the other hand, by including a specific polar solvent, the pigment-derived component is easily dissolved in the aqueous ink solution. Therefore, the effect of capturing the pigment-derived component by the DNA in the present invention becomes more effective.

[Application Example 6]
In the aqueous ink composition of any one of Application Examples 1 to 5,
Furthermore, at least 1 type of resin selected from the group which consists of a urethane resin, an acrylic resin, and a styrene-acrylate resin can be included.

  According to the water-based ink composition of Application Example 6, it is possible to improve the dispersion stability of the pigment and the fixing property to the recording medium.

[Application Example 7]
In the water-based ink composition of Application Example 6,
The ratio of the DNA content [Cd] and the solid content Σ [Cr] of the resin is 0.0.
The relationship of 02 ≦ [Cd] / Σ [Cr] ≦ 2 can be satisfied.

  If the content of DNA is too much with respect to the total solid content of the resin contained in the ink, a film-like thin film is easily formed on the surface of the image, and the abrasion resistance tends to be impaired. As in the aqueous ink composition of Application Example 7, when the content of DNA and resin is in a predetermined relationship, the formed image tends to have good abrasion resistance.

[Application Example 8]
In the aqueous ink composition of any one of Application Examples 1 to 7,
The pH can be 7 or more and 10 or less.

  According to the aqueous ink composition of Application Example 8, DNA can be stably dissolved in the aqueous ink solution, and the storage stability is further improved.

  Hereinafter, preferred embodiments of the present invention will be described. Embodiment described below demonstrates an example of this invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention.

1. Water-based ink composition The water-based ink composition according to this embodiment contains a pigment, a polar solvent, DNA, and water, and the total content Σ [Cp] of the polar solvent and the content of the DNA [ The ratio with respect to Cd] satisfies the relationship of 0.01 ≦ [Cd] / Σ [Cp] ≦ 5. Hereinafter, each component contained in the water-based ink composition according to this embodiment will be described.

  In the present invention, “DNA” refers to deoxyribonucleic acid, that is, nucleic acid composed of deoxyribose (pentose), phosphate, and base, and various functional groups outside the helical structure of deoxyribonucleic acid. It also includes “modified deoxyribonucleic acid” modified with lipids.

  Further, the “ink aqueous solution” in the present specification refers to an aqueous solution composed of a liquid component excluding a pigment in an aqueous ink composition.

1.1. Pigment The aqueous ink composition according to the present embodiment contains a pigment. Although it does not restrict | limit especially as a pigment seed | species, The pigment containing the molecule | numerator which has a planar skeleton can be used. Molecules having a planar structure are easily captured because they are intercalated inside the DNA helical structure described below.

  Here, the “planar skeleton” is not limited to the following, but for example, a condensed polycyclic skeleton such as naphthalene, anthracene, phenanthrene, and pyrene in which benzene is condensed in a plane, and a polycyclic ring such as porphyrin. Planar structures such as heteropolycyclic skeletons containing heterocycles such as nitrogen, oxygen, sulfur and phosphorus in the skeleton, and ring assembly skeletons in which two ring systems such as azobenzene and bicyclopentadienylidene are connected by a bond that maintains planarity A skeleton having a general conjugated system or a skeleton having planarity maintained by a conjugated system.

Therefore, the pigment has a planar skeleton as long as the dye molecule constituting the pigment has the skeleton described above, and the entire dye molecule does not have to have such a skeleton. Therefore, for example, even when one dye molecule has a plurality of planar skeletons, the dye molecule has a planar skeleton. Furthermore, the coloring material molecule of the coloring material does not need to be planar as a whole. For example, various substituents are arranged on a planar skeleton, and the substituent is out of the plane of the planar skeleton. It doesn't matter. Further, for example, a plurality of planar skeletons may not be along the same plane, and the planes of the planar skeletons may not be parallel to each other.

  Examples of such pigments include organic dye molecules that have a conjugated system and color by absorbing the energy of light. Examples of such pigments composed of organic dye molecules include azo pigments, phthalocyanine pigments, condensed polycyclic pigments, nitro pigments, nitroso pigments, quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, and anthrapyrimidines. Pigments, ansanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments Examples thereof include pigments, isoindolinone pigments, and azomethine pigments.

  The content of the pigment in the aqueous ink composition according to the present embodiment is not particularly limited, but is preferably 1% by mass or more and 20% by mass or less with respect to the total mass (100% by mass) of the aqueous ink composition. Preferably they are 2 mass% or more and 10 mass% or less, Most preferably, they are 3 mass% or more and 8 mass% or less.

  In the water-based ink composition according to this embodiment, from the viewpoint of uniformly and stably dispersing the pigment, it is preferable to use a resin-dispersed pigment or a self-dispersed pigment in which the pigment is dispersed with a resin.

1.1.1. Resin Dispersion Pigment The resin dispersant used in the resin dispersion pigment includes polyvinyl alcohols, polyacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer. Styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic Acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester Copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate Le - like acrylic acid copolymers and the salts thereof. Among these, a copolymer of a monomer having a hydrophobic functional group and a monomer having a hydrophilic functional group, and a polymer composed of a monomer having both a hydrophobic functional group and a hydrophilic functional group are preferable. As the form of the copolymer, any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer can be used.

  Examples of the salt include basic compounds such as ammonia, ethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, diethanolamine, triethanolamine, triisopropanolamine, aminomethylpropanol, and morpholine. Of the salt. The addition amount of these basic compounds is not particularly limited as long as it is equal to or more than the neutralization equivalent of the resin dispersant.

  The molecular weight of the resin dispersant is preferably in the range of 1,000 to 100,000 as the weight average molecular weight, and more preferably in the range of 3,000 to 10,000. When the molecular weight is in the above range, the pigment is more stably dispersed in water, and viscosity control when applied to the ink composition is easy.

A commercial item can also be used as a resin dispersing agent. Specifically, Joncryl 67 (weight average molecular weight: 12500, acid value: 213), Joncryl 678 (weight average molecular weight: 8,500, acid value: 215), Joncryl 586 (weight average molecular weight: 4) , 600, acid value: 108), joncryl 611 (weight average molecular weight: 8,100, acid value: 53), joncryl 680 (weight average molecular weight: 4,900, acid value: 215), joncryl 682 (weight) Average molecular weight: 1,700, acid value: 238), Joncryl 683 (weight average molecular weight: 8,000, acid value: 160), Joncryl 690 (weight average molecular weight: 16,500, acid value: 240) (above Trade name, manufactured by BASF Japan Ltd.).

  As a method for dispersing the resin-dispersed pigment in water, the above-mentioned pigment, resin dispersant, water, water-soluble organic solvent, neutralizer, etc. are added as necessary, and ball mill, sand mill, attritor, roll mill, agitator mill , Henschel mixers, colloid mills, ultrasonic homogenizers, jet mills, ong mills and the like. In this case, as the particle diameter of the pigment, it is possible to disperse until the average particle diameter is 20 nm or more and 500 nm or less, more preferably 40 nm or more and 200 nm or less, in order to ensure dispersion stability of the pigment in water. preferable.

  The amount of the resin dispersant added is preferably 10 parts by mass or more and 90 parts by mass or less, and more preferably 30 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the pigment. When the addition amount of the resin dispersant is within the above range, the dispersion stability of the pigment in water is further improved.

1.1.2. Self-dispersing pigment The water-based ink composition according to the present embodiment can contain a self-dispersing pigment as a pigment. By using the self-dispersing pigment, the viscosity of the water-based ink composition can be easily adjusted to an appropriate range, so that handling becomes easy. Further, the self-dispersing pigment can be uniformly dispersed in the water-based ink composition without separately adding a dispersant.

  The “self-dispersing pigment” in the present invention has at least one functional group selected from the group consisting of a carbonyl group, a carboxy group, an aldehyde group, a hydroxy group, a sulfone group, an ammonium group, and a salt thereof on the surface. Means a surface-modified pigment which is bonded directly or indirectly through an alkyl group, an aryl group or the like.

Self-dispersed pigments can be prepared by coordinating functional groups or molecules containing functional groups to the surface of the pigment, chemical bonding such as grafting, etc., by physical or chemical treatment such as vacuum plasma. Can be obtained. For example, it can be obtained by the method described in JP-A-8-3498. Moreover, as a self-dispersion pigment, it is also possible to use a commercial item, for example, "Microjet CW1", "Microjet CW2" manufactured by Orient Chemical Industry Co., Ltd., "CAB-O-" manufactured by Cabot Corporation. JET 200 "," CAB-O-JET
300 "or the like can be used.

  Hereinafter, a specific example of the method for preparing the self-dispersing pigment will be described. First, the above-mentioned pigment (pigment before surface modification) is added to the solvent, and this is subjected to high-speed shearing dispersion with a high-speed mixer or the like, or impact-dispersed with a bead mill or jet mill or the like to form a slurry pigment A dispersion is obtained. While slowly stirring the pigment dispersion, a treatment agent containing sulfur (sulfamic acid, fuming sulfuric acid, sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, etc.) is added, and the pigment dispersion is heated to 60 ° C. or higher and 200 ° C. or lower. The dispersibility-imparting group is introduced to the pigment surface by heat treatment. After removing the solvent from the pigment dispersion, self-dispersing pigment can be obtained by removing the treatment agent containing sulfur by repeating washing with water, ultrafiltration, reverse osmosis, centrifugation, filtration and the like. The average particle size of the self-dispersing pigment is preferably 20 nm or more and 500 nm or less, and more preferably 40 nm or more and 200 nm or less. This further improves the dispersion stability of the pigment in water.

1.2. Polar Solvent The water-based ink composition according to the present embodiment contains a polar solvent from the viewpoint of controlling wet spreading properties, penetrability, and drying properties on the recording medium. Since this polar solvent is an important component for controlling the characteristics of the ink, it is always contained in the aqueous ink solution. However, the ink aqueous solution containing a specific polar solvent shows solubility although the above-mentioned pigment-derived component is slight. It has been found that a part of the dissolved pigment-derived component is reprecipitated with a change in temperature environment to form crystalline foreign matters. This foreign matter gradually clogs the head filter, causing a problem of ink ejection failure. According to the water-based ink composition according to the present embodiment, such a problem can be solved by capturing the dissolved pigment-derived component with DNA described later.

  The specific polar solvent used in the water-based ink composition according to this embodiment includes at least one selected from the group consisting of alkanediols, alkylene glycol ethers, pyrrolidones, amides, and lactones. Solvent (hereinafter also referred to as “specific polar solvent”). Ink aqueous solutions containing such specific polar solvents tend to dissolve the above-mentioned pigment-derived components more easily than other solvents, and thus tend to cause the problem of ink ejection failure due to the above-mentioned foreign matter. Hereinafter, specific examples of the specific polar solvent that can be used in the water-based ink composition according to this embodiment will be listed.

(1) Alkanediols As alkanediols, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2 1,2-alkanediols such as octanediol; 1,3-butanediol, 1,3-pentanediol, 1,3-hexanediol, 1,3-heptanediol, 1,3-octanediol, etc. 3-alkanediol; 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2,2-diethyl-1,3- Propanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-ethyl- Other diols such as 1,3-hexanediol, 3-methyl-1,5-pentanediol, 2,5-hexanediol, and 2,3-dimethyl-1,4-butanediol are listed.

(2) Alkylene glycol ethers As alkylene glycol ethers, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol mono Ethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol di Ethylene glycol ethers such as methyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, ethylene glycol ethyl methyl ether, diethylene glycol ethyl methyl ether, triethylene glycol ethyl methyl ether; propylene glycol monomethyl And propylene glycol ethers such as ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monoethyl ether.

(3) Pyrrolidones As pyrrolidones, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone, N-butyl-2-pyrrolidone, 5-methyl- Examples include 2-pyrrolidone and 1- (2-hydroxyethyl) -2-pyrrolidone.

(4) Amides Examples of amides include dimethylformamide, dimethylacetamide, diethylformamide, diethylacetamide, ecamide M100 (trade name, manufactured by Idemitsu Kosan Co., Ltd.), ecamide B100 (trade name, manufactured by Idemitsu Kosan Co., Ltd.), and the like. It is done.

(5) Lactones As lactones, α-acetolactone, α-ethyllactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, ζ-enantiolactone, η-caprolactone, Examples include γ-valerolactone, γ-heptalactone, γ-nonalactone, β-methyl-δ-valerolactone, 2-butyl-2-ethylpropiolactone, α, α-diethylpropiolactone, and the like.

  The content of the polar solvent in the aqueous ink composition according to the present embodiment is preferably 0.1% by mass or more and 20% by mass or less, more preferably with respect to the total mass (100% by mass) of the aqueous ink composition. It is 0.5 mass% or more and 10 mass% or less.

1.3. DNA
The aqueous ink composition according to this embodiment contains DNA. The DNA and modified DNA are not particularly limited, and any of natural, fragmented and artificial can be used. In addition, DNA and modified DNA may have a normal double-stranded double helix structure, a triple-stranded triple helix structure, or a four-stranded structure. It may have a quadruple helix (quadruple helix) structure. The type of DNA can be appropriately selected depending on the type of molecule having a planar skeleton to be trapped, the type of solvent, and the like.

  DNA and modified DNA have a helical structure, and base pairs having a planar structure are tightly packed inside the helical structure. Since it has such a structure, DNA and modified DNA can intercalate molecules having a planar skeleton inside the helical structure, and trap molecules having a planar skeleton.

  DNA is water-soluble because of its high affinity with water on the outside of the helical structure. For example, molecular chains can be spread in water, and after trapping molecules with a planar structure, the state is further increased. Can exist stably.

  The modified DNA is obtained by modifying the outside of the DNA helical structure with various functional groups and lipids, and the polarity (hydrophilicity or lipophilicity) of the DNA can be appropriately set. For example, when the modified DNA is lipid-modified DNA and has a small polarity, it can exist without spreading in an organic solvent with a small polarity, and after trapping a molecule having a planar structure, Furthermore, it can exist stably in that state.

A phosphate group is located outside the helical structure of DNA and forms, for example, a counter ion with a cation. The counter cation of the phosphate group in DNA is preferably at least one selected from the group consisting of hydrogen ion, lithium ion, sodium ion, potassium ion, cesium ion, ammonium ion and tetraalkylammonium ion. Since the counter cation is such a cation species, DNA can be rapidly dissolved in the aqueous ink solution, so that the pigment-derived component dissolved in the aqueous ink solution can be effectively captured.

  In addition, although DNA has water solubility, a cationic polymer can be bound to a phosphate group in DNA (substitution with the above counter cation). At this time, when the polymer has a lipid such as an alkyl chain, the polymer is in a shape of wrapping DNA, and the lipid is arranged facing outward. Such lipid-modified DNA exhibits hydrophobicity according to the degree of modification, and can adjust the degree of hydrophilicity and hydrophobicity.

  The number of base pairs of DNA and modified DNA is not particularly limited as long as it can trap a molecule having a planar skeleton, and can be, for example, 10 base pairs or more and 100000000 base pairs or less.

  The solid content of DNA in the water-based ink composition according to this embodiment can be blended according to the concentration to be intercalated, that is, the expected concentration of the pigment-derived component dissolved in the ink aqueous solution. Preferably it is 0.001 mass% or more and 10 mass% or less with respect to the total mass (100 mass%) of an aqueous ink composition, More preferably, it is 0.005 mass% or more and 5 mass% or less, Most preferably, it is 0.01 mass. % To 4% by mass. When the solid content of DNA is in the above range, the pigment-derived component dissolved in the aqueous ink solution can be intercalated, and a thin film of DNA is not formed on the surface of the image to be formed, resulting in high abrasion resistance. It becomes good.

1.4. Water The water-based ink composition according to this embodiment contains water. As water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. The content of water in the aqueous ink composition according to this embodiment is preferably 30% by mass or more, more preferably 50% by mass or more and 95% by mass with respect to the total mass (100% by mass) of the aqueous ink composition. Hereinafter, it is particularly preferably 60% by mass or more and 90% by mass or less. Here, the content of water is not limited to the amount to which water is added, and when other additives are added, the water content in the additives is also included.

  In the present specification, the “aqueous” ink composition refers to an ink composition containing 30% by mass or more of water with respect to the total mass (100% by mass) of the aqueous ink composition.

1.5. Other components In addition to the above components, the water-based ink composition according to the present embodiment is a water-soluble organic solvent other than the specific polar solvent, a resin, a surfactant, a pH adjuster, a chelating agent, an antiseptic, and a viscosity adjuster. An agent, a dissolution aid, an antioxidant, an antifungal agent and the like may be contained.

1.5.1. Water-soluble organic solvent The water-soluble organic solvent other than the specific polar solvent is not particularly limited, and examples thereof include alcohols (for example, ethyl alcohol, 1-propanol, fluorinated alcohol, etc.) and glycerin of polyhydric alcohols. be able to. In particular, glycerin functions as a humectant and has an effect of making it more difficult to dry even if the aqueous ink composition is left in contact with air. These water-soluble organic solvents may be used alone or in combination of two or more. Alcohols and glycerin are solvents that are included in the category of polar solvents in a broad sense, but have poor ability to dissolve pigment-derived components. Therefore, alcohols and glycerin are not included in the concept of the polar solvent in the present invention.

When blending these water-soluble organic solvents, the content of the water-soluble organic solvent is preferably 0.1 to 30% by mass, more preferably 100% by mass when the total mass of the water-based ink composition is 100% by mass. Is 0.5 to 20% by mass. When the water-based ink composition contains the water-soluble organic solvent, the surface tension is lower than that of the water-based ink composition containing only water as a solvent. For example, each member of an ink jet recording apparatus (tube, ink cartridge, etc.) Increases wettability. Thereby, the trapping performance of foreign matter by DNA may be improved.

1.5.2. Resin The water-based ink composition according to this embodiment may contain a resin (hereinafter, also referred to as “fixing resin”) for fixing the above-described pigment to a recording medium. The fixing resin is preferably supplied in the form of water solubility, dispersion or emulsion.

  The fixing resin is not limited to these, but is preferably at least one resin selected from the group consisting of urethane resins, acrylic resins, and styrene-acrylate resins. By containing these fixing resins, the fixing property to the recording medium can be improved and the abrasion resistance is also improved.

  The urethane resin is not particularly limited as long as it has a urethane bond in the molecule, but in addition to the urethane bond, a polyether type urethane resin having an ether bond in the main chain, and a polyester type urethane having an ester bond in the main chain. Resin, polycarbonate-type urethane resin containing a carbonate bond in the main chain, and the like can also be used.

  As the fixing resin, a self-reactive urethane resin, acrylic resin, or styrene acrylate resin may be used. Examples of such a self-reactive resin include a urethane resin blocked with a blocking agent having a hydrophilic group; a blocked urethane resin provided with a hydrophilic segment; a functional group such as a carboxyl group, a hydroxyl group, an amino group, and a methylol group. An acrylic resin obtained by copolymerizing an acrylic monomer having

  Examples of commercially available urethane resin emulsions include Sancure 2710 (manufactured by Nippon Lubrizol), Permarin UA-150 (manufactured by Sanyo Chemical Industries), Superflex 150, 420, 460, 470, 610, 700 (or more, Dai-ichi Kogyo Seiyaku Co., Ltd.), NeoRez R-9660, R-9637, R-940 (above, manufactured by Enomoto Kasei Co., Ltd.), Adekabon titer HUX-380, 290K (above, made by ADEKA Corporation), Takerak ( R) W-605, W-635, WS-6021 (above, manufactured by Mitsui Chemicals, Inc.) and the like.

  Examples of commercially available styrene acrylate resins and acrylic resins include Mobile 966A, Mobile 7320 (manufactured by Nippon Synthetic Chemical Co., Ltd.), Microgel E-1002, Microgel E-5002 (above, Nippon Paint Co., Ltd.), and Boncoat 4001. Boncoat 5454 (above, manufactured by DIC Corporation), SAE1014 (manufactured by Zeon Corporation), Cybinol SK-200 (manufactured by Seiden Chemical Co., Ltd.), Jonkrill 7100, Jonkrill 390, Jonkrill 711, Jonkrill 511, John Krill 7001, John Krill 632, John Krill 741, John Krill 450, John Krill 840, John Krill 74J, John Krill HRC-1645J, John Krill 734, John Krill 852, John Krill 76 0, John Crill 775, John Crill 537J, John Crill 1535, John Crill PDX-7630A, John Crill 352J, John Crill 352D, John Crill PDX-7145, John Crill 538J, John Crill 7640, John Crill 7641, John Crill 631, Examples include Jonkrill 790, Jonkrill 780, Jonkrill 7610 (manufactured by BASF), NK binder R-5HN (manufactured by Shin-Nakamura Chemical Co., Ltd.), Paraloid B60 (manufactured by Rohm and Haas) and the like.

  The content of the fixing resin (solid content) in the aqueous ink composition according to this embodiment is preferably 0.1% by mass or more and 5% by mass or less with respect to the total mass (100% by mass) of the aqueous ink composition. More preferably, it is 0.5 mass% or more and 4 mass% or less.

1.5.3. Surfactant The water-based ink composition according to this embodiment may contain a surfactant. As the surfactant, any of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used, and these may be used in combination.

  The nonionic surfactant is preferably at least one selected from the group consisting of acetylene glycol surfactants, acetylene alcohol surfactants, fluorosurfactants, and polysiloxane surfactants. . These nonionic surfactants are excellent in the ability to appropriately maintain the surface tension and interfacial tension of the aqueous ink composition. Accordingly, the surface tension and the interfacial tension with the printer member in contact with the ink such as the head nozzle surface can be appropriately maintained. Therefore, when this is applied to the ink jet recording method, the ejection stability can be improved.

  Examples of the acetylene glycol surfactant and the acetylene alcohol surfactant include, but are not limited to, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7. , 9-tetramethyl-5-decyne-4,7-diol alkylene oxide adduct, and 2,4-dimethyl-5-decyn-4-ol and 2,4-dimethyl-5-decyn-4-ol, Selected from alkylene oxide adducts of 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3ol, 2,4-dimethyl-5-hexyn-3-ol One or more types can be exemplified. Commercially available acetylene glycol surfactants and acetylene alcohol surfactants can also be used. Surfynol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA (all trade names, manufactured by Air Products and Chemicals, Inc.), Orphine B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP. 4001, EXP. 4036, EXP. 4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.), acetylenol E00, E00P, E40, E100 (all trade names, Kawaken Fine Chemical Co., Ltd.).

  As the fluorosurfactant, commercially available ones may be used, and examples thereof include Megafac F-479 (manufactured by DIC Corporation), BYK-340 (manufactured by Big Chemie Japan), and the like.

  As the polysiloxane surfactant, commercially available ones can be used. For example, Olfine PD-501, Olfine PD-502, Olfine PD-570 (all manufactured by Nissin Chemical Industry Co., Ltd.), BYK -347, BYK-348 (both manufactured by Big Chemie Co., Ltd.) and the like.

Furthermore, examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, alkyl glucoside, polyoxyalkylene glycol alkyl ether, polyoxyalkylene glycol, polyoxyalkylene glycol alkyl phenyl ether, and sucrose. Fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, sorbitan fatty acid ester, polyoxyalkylene acetylene glycol, polyoxyalkylene glycol alkylamine, polyoxyethylene alkylamine, polyoxyethylene alkylamine oxide, fatty acid alkanolamide, Alkyrol amide, polyoxyethylene polyoxypropylene block It may also be used polymers, and the like.

  Among the nonionic surfactants, acetylene glycol surfactants are more preferable because they have particularly excellent ability to keep the surface tension and interfacial tension properly and have almost no bubble property. Can be used. That is, since the bubble property is small, for example, when the aqueous ink composition is applied to an ink jet recording apparatus, it is desirable that the bubbles are not easily fixed to the step portion of the ink flow path.

  Examples of the anionic surfactant include higher fatty acid salt, soap, α-sulfo fatty acid methyl ester salt, linear alkylbenzene sulfonate, alkyl sulfate ester salt, alkyl ether sulfate ester salt, monoalkyl phosphate ester salt, α -Olefin sulfonate, alkylbenzene sulfonate, alkyl naphthalene sulfonate, naphthalene sulfonate, alkane sulfonate, polyoxyethylene alkyl ether sulfate, sulfosuccinate, polyoxyalkylene glycol alkyl ether phosphate ester, etc. Is mentioned.

  Examples of the cationic surfactant include alkyltrimethylammonium salts, dialkyldimethylammonium salts and alkyldimethylbenzylammonium salts as quaternary ammonium series, and N-methylbishydroxyethylamine fatty acid ester hydrochloride as amine salt series.

  Examples of amphoteric surfactants include alkylamino fatty acid salts as amino acids, alkylcarboxyl betaines as betaines, and alkylamine oxides as amine oxides. The amphoteric surfactant is not limited to these.

  The content of the surfactant is preferably 0.1 to 2% by mass, more preferably 0.2 to 1% by mass, when the total mass of the aqueous ink composition is 100% by mass.

1.5.4. pH adjuster The aqueous ink composition according to the present embodiment may be adjusted to a pH of 7 to 10, preferably 8 to 9.5 by adding a pH adjuster. By setting the pH of the aqueous ink composition within the above range, the solubility of DNA in the aqueous ink solution increases, so the effect of capturing the pigment-derived component dissolved in the aqueous ink solution is enhanced. When the pH is less than 7 and the acid side is used, the solubility of DNA in an aqueous ink solution tends to be small, which is not preferable. A pH exceeding 10 is not preferable because the attack property to the member of the ink jet recording apparatus becomes strong.

  Examples of the pH adjuster include alkanolamines such as diethanolamine, triethanolamine, dimethylethanolamine, and diethylethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and lithium hydroxide; Examples include ammonium hydroxide; carbonates of alkali metals such as lithium carbonate, sodium carbonate, and potassium carbonate; aminosulfonic acids such as taurine;

1.5.5. Other compounds Known materials can be used for the chelating agent, preservative, viscosity modifier, dissolution aid, antioxidant, antifungal agent, and the like.

1.6. Content Ratio In the water-based ink composition according to this embodiment, the ratio of the total content Σ [Cp] of polar solvents to the content [Cd] of DNA is 0.01 ≦ [Cd] / Σ [Cp] ≦ 5. (Preferably 0.05 ≦ [Cd] / Σ [Cp] ≦ 1). If the value of [Cd] / Σ [Cp] is within the above range, the DNA can capture the pigment-derived component dissolved in the aqueous ink solution containing the polar solvent, and suppress the generation of crystalline foreign matter, Storage stability is improved. Further, by suppressing the occurrence of crystalline foreign matters in the aqueous ink composition, clogging due to foreign matters in the head filter is eliminated, and ink ejection stability is improved. When the value of [Cd] / Σ [Cp] is less than 0.01, since the content of DNA with respect to the polar solvent is small, the effect of capturing the pigment-derived component dissolved in the aqueous ink solution becomes small. For this reason, part of the pigment-derived component may reprecipitate due to a change in temperature environment or the like to form foreign matter, which may cause ink ejection failure. On the other hand, when the value of [Cd] / Σ [Cp] exceeds 5, since the content of DNA with respect to the polar solvent is large, there is no problem in the effect of capturing the pigment-derived component dissolved in the aqueous ink solution. A crisp film-like thin film is likely to be formed on the surface, and the rubbing resistance of the image may be impaired.

  The ratio of the DNA content [Cd] and the resin solid content Σ [Cr] preferably satisfies the relationship of 0.002 ≦ [Cd] / Σ [Cr] ≦ 2. More preferably, the relationship of ≦ [Cd] / Σ [Cr] ≦ 1 is satisfied. If the content of DNA is too much relative to the total solid content of the resin contained in the ink, a film-like thin film derived from DNA is likely to be formed on the surface of the image, and the rubbing resistance of the image is increased. There is a tendency to be damaged. Therefore, when the value of [Cd] / Σ [Cr] is within the above range, the formed image tends to have good abrasion resistance.

1.7. Physical Properties When the water-based ink composition according to this embodiment is used as an inkjet ink, the viscosity (viscosity at 25 ° C.) is preferably 2 mPa · s or more and 20 mPa · s or less, for example, by adjusting the composition or blending. Preferably they are 3 mPa * s or more and 15 mPa * s or less. As a result, the ejection stability (e.g., ejection volume stability, flight characteristics of droplets), ejection response (response speed, high frequency compatibility (frequency characteristics), etc.), etc., of the inkjet ink are excellent. it can. The viscosity of the ink for inkjet is JIS using a vibration viscometer.
It can obtain | require by the measurement based on Z8809.

1.8. Action Effect, etc. The aqueous ink composition according to the present embodiment can intercalate and capture pigment-derived components dissolved in an aqueous ink solution with DNA (deoxyribonucleic acid and / or modified deoxyribonucleic acid). Accordingly, the pigment-derived component dissolved in the ink aqueous solution can be removed or reduced, and foreign matter based on the pigment-derived component is hardly generated, so that the storage stability is improved.

In DNA, two polynucleotides form a double helix structure. In this polynucleotide, there are nucleobases (adenine, thymine, cytosine, guanine), and the sequence of one polynucleotide is adenine (A), thymine (T), cytosine (C), guanine (G). When the other polynucleotide has a sequence of thymine (T), adenine (A), guanine (G), and cytosine (C), AT, TA, CG, GC Complementary hydrogen bonds are formed in combination. Since the nucleobase has an aromatic ring and the above hydrogen bond is planar, π-π stacking is performed between adjacent aromatic ring planar rings of AT, TA, CG, and GC. To form a double helix. Thus, during π-π stacking, pigment-derived components (molecules having a planar skeleton) dissolved in the aqueous ink solution are inserted and stabilized. Therefore, it is considered that the crystal growth is suppressed because it is incorporated into DNA before the nucleus growth of the crystal.

  Further, when the total content Σ [Cp] of the polar solvent in the aqueous ink composition is large, the amount of the pigment-derived component dissolved in the aqueous ink solution also increases. In this case, it is only necessary to increase the content of DNA in the aqueous ink composition. However, if the content of DNA is increased, a film-like thin film made of DNA is easily formed on the surface of the image. There is a tendency that the abrasion resistance of the image is impaired. Therefore, in the present invention, the ratio of the total polar solvent content Σ [Cp] and the DNA content [Cd] in the aqueous ink composition is defined as 0.01 ≦ [Cd] / Σ [Cp] ≦ 5. doing. As a result, it is possible not only to suppress the generation of crystalline foreign substances derived from the pigment, but also to form an image having excellent abrasion resistance.

2. EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

2.1. Preparation of aqueous ink composition (1) Preparation of pigment dispersion In a reaction vessel, 20 parts of methyl ethyl ketone and 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol), 200 parts of a monomer mixture (26 parts of methacrylic acid, styrene) 10 parts of a mixture of 20 parts of a macromer, 74 parts of styrene, 20 parts of benzyl methacrylate, and 60 parts of 50POEP-800B) were mixed and sufficiently substituted with nitrogen gas to obtain a mixed solution.

  On the other hand, the remaining 90% of the monomer mixture was charged into a dropping funnel, and 0.27 part of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone and a radical polymerization initiator (2,2′-azobis (2,4-dimethylvalero). Nitrile)) 1.2 parts were added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.

  Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution obtained by dissolving 0.3 part of the radical polymerization initiator in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and 70 ° C. for 2 hours to obtain a polymer solution. It was. The weight average molecular weight of the obtained polymer was 120,000.

The details of the monomer are as follows.
-Styrene macromer; Styrene macromer, manufactured by Toa Gosei Co., Ltd., trade name: AS-6 (S), number average molecular weight 6000, polymerizable functional group: methacryloyloxy group-50POEP-800B; octoxy polyethylene glycol polypropylene glycol monomethacrylate (Ethylene oxide average added mole number = 8, propylene oxide average added mole number = 6, terminal: 2-ethylhexyl group): manufactured by Nippon Oil & Fat Co., Ltd., trade name: BLEMER 50POEP-800B

  23 parts of the polymer obtained by drying the obtained polymer solution under reduced pressure was dissolved in 70 parts of methyl ethyl ketone, and the neutralizing agent (5N aqueous sodium hydroxide solution) was neutralized at 60% and 230 parts of ion-exchanged water. In addition, the salt-forming group was neutralized, and 77 parts of a diazo pigment (C.I. Pigment Yellow 74 [P.Y.74], manufactured by Sanyo Dye Co., Ltd., trade name: FY7413) was added as a yellow pigment. At 20 ° C. for 1 hour. The obtained mixture was subjected to 10-pass dispersion treatment at a pressure of 200 MPa with a microfluidizer (trade name, manufactured by Microfluidics) to obtain a dispersion.

  After adding 250 parts of ion-exchanged water to the obtained dispersion and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2). .5 cm, manufactured by Fuji Photo Film Co., Ltd.) and filtered with a 25 mL needleless syringe (made by Terumo Co., Ltd.) to remove coarse particles, whereby the pigment-containing graft polymer particles having a solid content concentration of 20% An aqueous dispersion was obtained.

(2) Preparation of water-based ink composition Next, a polar solvent, glycerin, DNA, surfactant, fixing resin, and ion-exchanged water are added to the pigment dispersion obtained above so as to have the composition shown in Table 1. did. Thereafter, the mixture was stirred at room temperature for 1 hour, further filtered through a membrane filter having a pore size of 5 μm, and then degassed using a vacuum pump to obtain each aqueous ink composition used in Examples and Comparative Examples. In addition, the numerical value in Table 1 represents content (mass%) in ink, and the abbreviation of each component shown in Table 1 is as follows.

<Fixing resin>
・ Styrene-acrylate resin (Brand name “Johncrill 538J”, manufactured by BASF)
・ Urethane resin (trade name “M-1064”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
<Surfactant>
Surfynol 104 (trade name, manufactured by Air Products and Chemicals, Inc., acetylene glycol surfactant)
・ Orphine E1010 (trade name, manufactured by Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant)

2.2. Evaluation of aqueous ink composition (1) Evaluation of crystalline foreign matter After 40 g of each aqueous ink composition obtained above was put in a 50 cc glass bottle and sealed, these glass bottles were placed in a 20 ° C. environment for 2 months. I left it alone. Thereafter, when the ink left for two months was passed through a SUS filter provided with a plurality of holes of φ10 μm, C.I. I. Crystalline foreign matters derived from Pigment Yellow 74 remained on the filter. By counting the number of crystalline foreign matters, the state of occurrence of crystalline foreign matters was evaluated. The evaluation criteria are as follows. The evaluation results are also shown in Table 1.
A: The number of crystalline foreign substances is less than 20.
B: The number of crystalline foreign matters is 20 or more and less than 50.
C: The number of crystalline foreign matters is 50 or more.

(2) Evaluation of rubbing resistance Ink jet printer (product name “PX-G930”, manufactured by Seiko Epson Corporation, nozzle resolution: 180 dpi), which is an ink jet recording type printer, the aqueous ink composition of Examples or Comparative Examples in the head The product was filled. After filling, on the photographic paper (Seiko Epson Co., Ltd.), the aqueous ink compositions of the above Examples and Comparative Examples were recorded at a given amount per unit area of the recording medium: 1.86 mg / cm ² , A recorded material was produced. About the produced recorded matter of each Example and a comparative example, the gold width was mounted on the printing surface of the recorded matter which passed for 1 hour after printing, and also 50 g of weight was mounted on it. The gold width under the weight was pulled out, the degree of transfer to the drawn gold width was visually observed, and the abrasion resistance was evaluated according to the following criteria.
A: Transfer is not recognized at all.
B: Slight transfer is observed.
C: Transcription is clearly recognized.

2.3. Evaluation Results Table 1 below shows the compositions and evaluation results of the water-based ink compositions of the examples and comparative examples.

  As apparent from the results in Table 1, according to the aqueous ink composition of the present invention, C.I. It was found that the occurrence of crystalline foreign matters can be effectively reduced by intercalating I pigment yellow 74 with DNA. At the same time, it has been found that by adjusting the balance between the DNA content and the polar solvent content in the water-based ink composition, the abrasion resistance of the formed image is improved.

  According to Examples 1 to 6, the ratio between the total content Σ [Cp] of the polar solvent and the content [Cd] of the DNA is a predetermined relationship (0.01 ≦ [Cd] / Σ [Cp] ≦ 5), it is possible to reduce the generation of crystalline foreign matters and improve the abrasion resistance of the image, but the DNA content [Cd] and the resin solid content Σ [ It was found that the higher the ratio with [Cr] ([Cd] / Σ [Cr]), the more the image abrasion resistance tends to be impaired.

  In addition, from the results of Comparative Examples 1 to 3, if the ratio of the total content Σ [Cp] of polar solvents to the content [Cd] of DNA ([Cd] / Σ [Cp]) is less than 0.01, It has been found that the effect of capturing the pigment-derived component is insufficient, and if it exceeds 5, the abrasion resistance of the image tends to be impaired.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

Claims (8)

Containing a pigment, a polar solvent, DNA, and water;
A ratio of the total content Σ [Cp] of the polar solvent and the content [Cd] of the DNA satisfies a relationship of 0.01 ≦ [Cd] / Σ [Cp] ≦ 5. Ink composition.   The aqueous ink composition according to claim 1, wherein the pigment is a resin-dispersed pigment.   The water-based ink composition according to claim 1, wherein the pigment is a self-dispersing pigment.   The counter cation of the phosphate group in the DNA is at least one selected from the group consisting of hydrogen ion, lithium ion, sodium ion, potassium ion, cesium ion, ammonium ion, and tetraalkylammonium ion. The water-based ink composition according to any one of claims 3 to 4.   The said polar solvent contains at least 1 sort (s) selected from the group which consists of alkanediols, alkylene glycol ethers, pyrrolidones, amides, and lactones as described in any one of Claims 1 thru | or 4. A water-based ink composition.   The aqueous ink composition according to any one of claims 1 to 5, further comprising at least one resin selected from the group consisting of a urethane resin, an acrylic resin, and a styrene-acrylate resin.   The ratio between the content [Cd] of the DNA and the solid content Σ [Cr] of the resin satisfies a relationship of 0.002 ≦ [Cd] / Σ [Cr] ≦ 2. A water-based ink composition.   The aqueous ink composition according to any one of claims 1 to 7, wherein the pH is 7 or more and 10 or less.