JP2016199677A - Aqueous ink, ink cartridge, and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink which can record images realizing both high optical density and marker resistance regardless of types of record media.SOLUTION: An inkjet aqueous ink contains a self-dispersing pigment and a dye. The self-dispersing pigment is a pigment in which an anionic group is bound to a particle surface via another atomic group. The dye contains a compound represented by the following general formula (I).SELECTED DRAWING: None

Description

  The present invention relates to an aqueous ink, an ink cartridge, and an ink jet recording method.

  The black ink used in the ink jet recording method is required to have image performance such as being able to record an image having a high optical density and recording an image having marker resistance. Specifically, the above-mentioned image performance is required without depending on the type of the recording medium in the case of plain paper that is frequently used for text recording among the recording media. Among the recording media, in particular, plain paper includes various types having different ink permeability. In particular, in a recording medium with high ink permeability, the optical density of an image recorded with ink tends to decrease. In addition, in a recording medium with low ink permeability, the marker resistance of an image recorded with ink tends to decrease.

  For example, Patent Document 1 discloses an image obtained by using an ink containing a self-dispersing pigment in which a functional group having high reactivity with calcium is bonded to the surface of pigment particles based on a calcium index value that defines an index of reactivity with calcium. There are proposals for improving the optical density of the. Japanese Patent Application Laid-Open No. 2004-228561 has a proposal regarding achieving both optical density and gas resistance of an image by using a self-dispersing pigment and a dye having a predetermined structure in combination.

Special table 2009-515007 JP 2006-63332 A

  As described in Patent Documents 1 and 2, various proposals have been made so far for improving the optical density of an image recorded with ink. However, no detailed study has been made on the marker resistance of an image recorded using an ink containing a pigment and a dye. For example, the use of the self-dispersing pigment described in Patent Document 1 can be expected to improve optical density in a recording medium with low ink permeability, but it has been found that there is room for improvement in marker resistance. . Furthermore, it has been found that a sufficient optical density cannot still be obtained in a recording medium having a high ink permeability. Further, it was found that even when a self-dispersing pigment and a dye are used in combination as in the ink described in Patent Document 2, an improvement in optical density can be expected, but the marker resistance is not at a sufficient level.

  Accordingly, an object of the present invention is to provide a water-based ink capable of recording an image having both high optical density and marker resistance regardless of the type of recording medium. Another object of the present invention is to provide an ink cartridge and an ink jet recording method using the water-based ink.

  The above object is achieved by the present invention described below. That is, according to the present invention, there is provided an aqueous inkjet ink containing a self-dispersing pigment and a dye, wherein the self-dispersing pigment has a structure in which an anionic group is bonded to the particle surface via another atomic group. There is provided an aqueous ink, which is a pigment having a functional group, and wherein the dye contains a compound represented by the following general formula (I).

（前記一般式（Ｉ）中、Ｒ₁及びＲ₃は、それぞれ独立に、水素原子、ハロゲン原子、シアノ基、ヒドロキシ基、カルボン酸基、スルホン酸基、ホスホン酸基、スルファモイル基、Ｎ−アルキルアミノスルホニル基、Ｎ−フェニルアミノスルホニル基、炭素数１乃至４のアルキルスルホニル基（ヒドロキシ基で置換されていてもよい）、ニトロ基、アシル基、ウレイド基、炭素数１乃至４のアルキル基（ヒドロキシ基又は炭素数１乃至４のアルコキシ基で置換されていてもよい）、炭素数１乃至４のアルコキシ基（ヒドロキシ基、炭素数１乃至４のアルコキシ基、スルホン酸基、又はカルボン酸基で置換されていてもよい）、アシルアミノ基、アルキルスルホニルアミノ基、又はフェニルスルホニルアミノ基（フェニル部分は、ハロゲン原子、炭素数１乃至４のアルキル基、又はニトロ基で置換されていてもよい）を表し、Ｒ₂は、水素原子又はスルホン酸基を表し、ｎは、０又は１を表し、Ｍは、それぞれ独立に、水素原子、アルカリ金属、アンモニウム、又は有機アンモニウムを表す）

(In the general formula (I), R ₁ and R ₃ are each independently a hydrogen atom, halogen atom, cyano group, hydroxy group, carboxylic acid group, sulfonic acid group, phosphonic acid group, sulfamoyl group, N-alkyl. An aminosulfonyl group, an N-phenylaminosulfonyl group, an alkylsulfonyl group having 1 to 4 carbon atoms (which may be substituted with a hydroxy group), a nitro group, an acyl group, a ureido group, an alkyl group having 1 to 4 carbon atoms ( An optionally substituted hydroxy group or an alkoxy group having 1 to 4 carbon atoms), an alkoxy group having 1 to 4 carbon atoms (hydroxy group, an alkoxy group having 1 to 4 carbon atoms, a sulfonic acid group, or a carboxylic acid group). Optionally substituted), an acylamino group, an alkylsulfonylamino group, or a phenylsulfonylamino group (the phenyl moiety is a halogen atom, R ₂ represents a hydrogen atom or a sulfonic acid group, n represents 0 or 1, and M represents an independent group, which may be substituted with an alkyl group having 1 to 4 carbon atoms or a nitro group. Represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium)

  According to the present invention, it is possible to provide a water-based ink capable of recording an image having both high optical density and marker resistance regardless of the type of recording medium. In addition, according to the present invention, an ink cartridge and an ink jet recording method using this water-based ink can be provided.

It is sectional drawing which shows typically one Embodiment of the ink cartridge of this invention. FIG. 2 is a diagram schematically illustrating an example of an ink jet recording apparatus used in the ink jet recording method of the present invention, in which (a) is a perspective view of a main part of the ink jet recording apparatus, and (b) is a perspective view of a head cartridge.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is dissociated into ions in the ink, but is expressed as “contains a salt” for convenience. In addition, water-based ink for inkjet may be simply referred to as “ink”.

  First, in order to obtain an image having a high optical density, it is necessary that a large amount of color material be present on or near the surface of the recording medium. Since the dye easily penetrates into the recording medium and is difficult to stay on the surface as compared with the pigment, a large amount of the pigment has heretofore been used to improve the optical density of the image on plain paper.

  Among pigments, a self-dispersing pigment having a structure in which an anionic group is bonded to the particle surface via another atomic group (hereinafter, simply referred to as “pigment”) It is susceptible to effects such as evaporation and penetration of liquid components after being applied to the recording medium. Further, when a salt is added to an ink containing a self-dispersing pigment, the influence of the above becomes more prominent, and thus aggregation of the pigment is easily promoted. That is, according to the ink containing the self-dispersing pigment and the salt, it is easy to increase the optical density of an image even on a recording medium having high ink permeability. However, on the other hand, in such a recording medium, ink has low penetrability, and a large amount of pigment remains on the surface of the recording medium due to the promotion of pigment aggregation. This is because the pigment remaining on the surface of the recording medium is scraped by contact with the marker pen. Therefore, in order to improve the marker resistance while containing a salt, the content of the pigment must be reduced, but in this case, an image having a high optical density cannot be obtained.

  On the other hand, since dyes are water-soluble, images recorded with inks containing dyes tend to have low marker resistance. However, if most of the dye penetrates into the recording medium, the marker resistance may be reduced. The impact is considered small. However, if the content of the dye in the ink is increased in order to improve the optical density of the image recorded with the ink, the dye is also present near the surface of the recording medium. It turns out that it falls. From the above, it has been found that it is difficult to obtain an image having both high optical density and marker resistance regardless of the type of recording medium with an ink containing only a pigment or only a dye as a coloring material. .

  The present inventors have studied an ink that can achieve both high optical density and marker resistance regardless of the type of recording medium. As a result, when an ink containing a self-dispersing pigment is used, the effect of improving the optical density is remarkably exhibited by using the self-dispersing pigment together with the compound represented by the general formula (I) which is a dye. I understood. In addition, the present inventors have found that when this ink is used, the marker resistance in a recording medium having low ink permeability is also improved, and the present invention has been completed.

  As a result of further investigations, the present inventors have used a dye that has good color development on plain paper and has little adsorption to the pigment in order to obtain an image having high optical density and marker resistance. I found it necessary to do. The inventors presume this reason as follows.

  As described above, in order to obtain an image having a high optical density, it is necessary to make more color materials exist on or near the surface of the recording medium. When self-dispersing pigments and dyes are used in combination as coloring materials, the dye that has previously penetrated into the recording medium exerts the action of retaining the recording medium, so that more pigment can be present on the surface of the recording medium. become. For this reason, it is estimated that an image having a high optical density can be obtained. In addition, since the optical density at this time is also related to the color developability of the dye, the color developability of the dye needs to be good, and it is considered necessary to select the structure of the dye. By selecting a dye having high color developability, a high optical density can be maintained even if the pigment content is reduced as compared with a general aqueous ink containing a pigment. Further, when the dye is adsorbed to a certain extent, the aggregation of the pigment is inhibited, so that an image having a high optical density cannot be obtained particularly on a recording medium having a high ink permeability. Therefore, it is necessary to use a dye with little adsorption to the pigment.

  Another reason for using a dye that is less adsorbed to the pigment is a further improvement in marker resistance. In a recording medium with low ink permeability, the pigment tends to remain on the surface of the recording medium, and the dye penetrates into the recording medium. Therefore, the marker resistance is considered to depend on the performance of the pigment. Therefore, when a dye that easily adsorbs to the pigment is used, a large amount of the dye is present together with the pigment on or near the surface of the recording medium. Therefore, when the pigment is scraped by the marker pen, the dye also contacts the marker pen. Therefore, it turned out that marker resistance falls. On the other hand, it is presumed that a dye with little adsorption to the pigment has better marker resistance because most of the dye penetrates into the recording medium and less dye is present near the surface of the recording medium.

  As a result of the study by the present inventors, it was found that the compound represented by the general formula (I) has little adsorption to the pigment among black dyes. The reason for this is that the compound represented by the general formula (I) has a nitro group in addition to the sulfonic acid group, so that the hydrophilicity is higher and the particle surface is hydrophobic. It is speculated that the adsorption of is decreasing.

<Ink>
The aqueous ink for inkjet according to the present invention contains a self-dispersing pigment and a dye. Hereinafter, the components constituting the ink of the present invention and the physical properties of the ink will be described in detail.

(Pigment)
Examples of the pigment include organic pigments and inorganic pigments such as carbon black, and any of those usable for ink jet inks can be used. In the present invention, a black ink using carbon black as a pigment is preferable.

  The self-dispersing pigment used in the ink of the present invention is a pigment having a functional group having a structure in which an anionic group is bonded to the particle surface through another atomic group. By using this self-dispersing pigment, it is not necessary to add a dispersant for dispersing the pigment in the ink, or the amount of the dispersant added can be reduced.

Examples of the anionic group include a carboxylic acid group (—COOM), a sulfonic acid group (—SO ₃ M), and a phosphonic acid group (—PO (OM) ₂ ). M represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium each independently. Examples of the alkali metal include lithium, sodium, and potassium. Organic ammonium includes alkylamines having 1 to 3 carbon atoms such as methylamine and ethylamine; 1 carbon atoms such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine. Examples of the mono-, di- or trialkanolamines are 4 or less. In the present invention, M is preferably an alkali metal, more preferably potassium.

In the ink, if anionic groups such as carboxylic acid groups (—COOM), sulfonic acid groups (—SO ₃ M), and phosphonic acid groups (—PO (OM) ₂ ) are in salt form, some of them Either a dissociated state or a completely dissociated state may be used. That is, taking the phosphonic acid group (—PO (OM) ₂ ) as an example, the phosphonic acid group (—PO (OM) ₂ ) is represented by —PO ₃ H ₂ (free acid type), —PO ₃ H ⁻ M ^+. (Monobasic salt) and -PO ₃ ^2- (M ⁺ ) ₂ (dibasic salt) can take any form.

In the present invention, among self-dispersing pigments, it is preferable to use a pigment in which the anionic group is —PO (OM) ₂ , and the functional group includes _two phosphonic acid groups (—PO (OM) ₂ ). It is more preferable to use a bisphosphonic acid type self-dispersing pigment. Even if a monophosphonic acid type self-dispersing pigment having one phosphonic acid group as the functional group is used, it is of course possible to improve the optical density of an image. However, by using a bisphosphonic acid type self-dispersing pigment, the ink can be evaporated. Stability can be further improved. When a trisphosphonic acid type self-dispersing pigment is used, the storage stability of the ink may not be sufficiently obtained. Moreover, when the anionic group is directly bonded to the particle surface, the effect of improving the optical density by the combined use with the compound (dye) represented by the general formula (I) may not be obtained.

The other atomic group existing between the particle surface of the pigment and the anionic group is not particularly limited. Specific examples of other atomic groups include linear or branched alkylene groups having 1 to 12 carbon atoms, arylene groups such as phenylene groups and naphthylene groups, amide groups, sulfonyl groups, amino groups, imino groups, carbonyl groups. Groups, ester groups, ether groups and the like. Moreover, the group which combined these groups may be sufficient. Furthermore, it is preferable that the other atomic group includes at least one of an alkylene group and an arylene group and a group having hydrogen bonding properties (an amide group, a sulfonyl group, an amino group, a carbonyl group, an ester group, an ether group). . More preferably, the other atomic group contains —C ₆ H ₄ —CONH— (benzamide structure).

When the functional group of the self-dispersing pigment includes two phosphonic acid groups (—PO (OM) ₂ ), the functional group of the self-dispersing pigment includes a structure of —CQ (PO (OM) ₂ ) ₂ Is preferred. Here, -CQ- in the above formula is a part of the other atomic group, and Q is H, R, OR, SR, or N (R) ₂ (R is independently an alkyl group, an acyl group, Represents a group, an aralkyl group, or an aryl group. When R is a group containing a carbon atom, the number of carbon atoms is preferably 1-18. Specific examples of the group containing a carbon atom include alkyl groups such as methyl group and ethyl group; acyl groups such as acetyl group and benzoyl group; aralkyl groups such as benzyl group; aryl groups such as phenyl group and naphthyl group. be able to. Among these, it is more preferable that the structure of —CH (PO (OM) ₂ ) ₂ in which Q in the formula is a hydrogen atom is included in the functional group. In the present invention, a self-dispersing pigment having a functional group structure of —C ₆ H ₄ —CONH—CH— (PO (OM) ₂ ) ₂ is more preferable.

When a pigment having a functional group in which an anionic group such as a phosphonic acid group (—PO (OM) ₂ ) is bonded to the pigment particle surface via another atomic group is used, it is included as a filler in the recording medium. Aggregation of the pigment is further promoted by the interaction with calcium. Furthermore, since the aggregation of the pigment due to the interaction between the phosphonic acid group and calcium proceeds rapidly, the aggregate of the pigment becomes large. As a result, it was found that the surface of the image can be roughened, the effect of reducing the reflected light by increasing the absorption of light can be obtained, and an image having a higher optical density can be obtained. In order to obtain such an effect at a higher level, the introduction amount of the functional group containing a phosphonic acid group is preferably 0.10 mmol / g or more and 0.33 mmol / g or less with respect to 1 g of the pigment. It has been found that when the amount of the functional group containing a phosphonic acid group is less than 0.10 mmol / g, the amount of dye adsorbed on the pigment increases, and the marker resistance may be lowered. Further, it was found that when the amount of the functional group containing a phosphonic acid group is more than 0.33 mmol / g, the pigment may not easily aggregate and a higher optical density may not be obtained. The amount of functional groups introduced is the number of millimoles of functional groups per gram of solid content of the self-dispersing pigment.

  The introduction amount of the functional group containing a phosphonic acid group of the self-dispersing pigment can be measured by quantifying phosphorus as follows. Specifically, first, the pigment dispersion is diluted with pure water so that the content of the pigment (solid content) becomes a predetermined amount (for example, about 0.03% by mass) to prepare solution A. In addition, the pigment dispersion is subjected to ultracentrifugation under predetermined conditions (for example, conditions of 5 ° C., 80,000 rpm, 15 hours), the supernatant liquid from which the pigment has been removed is collected, and this is several tens of times with pure water Dilute to about (for example, 80 times) to prepare solution B. With respect to the obtained A liquid and B liquid, phosphorus is quantified by an ICP emission spectroscopic analyzer or the like, and the amount of phosphonic acid groups is calculated from the difference in phosphorus amount obtained from the measured values for these A liquid and B liquid. be able to. The introduction amount of the functional group containing a phosphonic acid group is the amount of phosphonic acid group / n (n represents the number of phosphonic acid groups contained in one functional group, 1 for mono, 2 for bis, 3 for tris. Can be calculated. Here, the number of phosphonic acid groups contained in the functional group can be known by analyzing the structure of the functional group by an analysis method such as NMR. In addition, although the method of measuring the introduction amount of the functional group containing a phosphonic acid group using a pigment dispersion liquid was described, it can measure similarly even if it uses ink. Further, the method for measuring the introduction amount of the functional group containing a phosphonic acid group is not limited to the method described above.

  The content (% by mass) of the self-dispersing pigment in the ink is preferably from 0.1% by mass to 15.0% by mass, more preferably from 0.5% by mass to 10% by mass, based on the total mass of the ink. 0.0 mass% or less.

  The ink of the present invention may contain another pigment other than the self-dispersing pigment for the purpose of color matching of the ink.

(dye)
The ink of the present invention contains a dye (coloring material) containing a compound represented by the following general formula (I).

In general formula (I), R ₁ and R ₃ each independently represent a hydrogen atom, a halogen atom, a cyano group, a hydroxy group, a carboxylic acid group, a sulfonic acid group, a phosphonic acid group, a sulfamoyl group, or an N-alkylaminosulfonyl group. Group, N-phenylaminosulfonyl group, alkylsulfonyl group having 1 to 4 carbon atoms (which may be substituted with hydroxy group), nitro group, acyl group, ureido group, alkyl group having 1 to 4 carbon atoms (hydroxy group) Or optionally substituted with an alkoxy group having 1 to 4 carbon atoms), an alkoxy group having 1 to 4 carbon atoms (substituted with a hydroxy group, an alkoxy group having 1 to 4 carbon atoms, a sulfonic acid group, or a carboxylic acid group). An acylamino group, an alkylsulfonylamino group, or a phenylsulfonylamino group (the phenyl moiety is a halogen atom, a carbon number) 1 to 4 alkyl groups or a nitro group optionally substituted).

  Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  The number of carbon atoms of the alkyl moiety in the N-alkylaminosulfonyl group is preferably 1 to 4. Examples of the N-alkylaminosulfonyl group include N-methylaminosulfonyl group, N-ethylaminosulfonyl group, N- (n-butyl) aminosulfonyl group, N, N-dimethylaminosulfonyl group, N, N-di (n -Propyl) aminosulfonyl group and the like.

  The alkylsulfonyl group having 1 to 4 carbon atoms which may be substituted with a hydroxy group includes a substituted or unsubstituted alkylsulfonyl group having 1 to 4 carbon atoms. Examples of the alkylsulfonyl group include unsubstituted alkylsulfonyl groups such as methylsulfonyl, ethylsulfonyl, propylsulfonyl and butylsulfonyl; substituted alkylsulfonyl groups such as hydroxyethylsulfonyl and 2-hydroxypropylsulfonyl.

  The acyl group includes an aliphatic acyl group. The number of carbon atoms of the alkyl moiety in the acyl group is preferably 1 to 4. Examples of the acyl group include acetyl, propionyl, butyryl, isobutyryl and the like.

  The alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxy group or an alkoxy group having 1 to 4 carbon atoms includes a substituted or unsubstituted alkyl group and a linear or branched alkyl group. . Here, the carbon number in the alkyl group having 1 to 4 carbon atoms refers to the carbon number in the case of unsubstituted. Therefore, the alkyl group having 1 to 4 carbon atoms substituted by the alkoxy group having 1 to 4 carbon atoms may have more than 4 carbon atoms as a whole. Examples of the alkyl group include unsubstituted alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl; 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, Examples include substituted alkyl groups such as methoxyethyl, 2-ethoxyethyl, n-propoxyethyl, isopropoxyethyl, n-butoxyethyl, methoxypropyl, ethoxypropyl, n-propoxypropyl, isopropoxybutyl, and n-propoxybutyl. Can do.

  The alkoxy group having 1 to 4 carbon atoms includes a substituted or unsubstituted alkoxy group, and the alkyl part in the alkoxy group is a hydroxy group, an alkoxy group having 1 to 4 carbon atoms, a sulfonic acid group, or a carboxylic acid group. May be substituted. Here, the number of carbon atoms in the alkoxy group having 1 to 4 carbon atoms refers to the number of carbon atoms when unsubstituted. Therefore, the alkoxy group having 1 to 4 carbon atoms in which the alkyl group in the alkoxy group is substituted may have more than 4 carbon atoms as a whole. Examples of the alkoxy group include unsubstituted alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy; 2-hydroxyethoxy, 2-hydroxypropoxy, 3-hydroxypropoxy, methoxy Ethoxy, ethoxyethoxy, n-propoxyethoxy, isopropoxyethoxy, n-butoxyethoxy, methoxypropoxy, ethoxypropoxy, n-propoxypropoxy, isopropoxybutoxy, n-propoxybutoxy, 2-hydroxyethoxyethoxy, carboxymethoxy, 2- Examples thereof include substituted alkoxy groups such as carboxyethoxy, 3-carboxypropoxy, 3-sulfopropoxy and 4-sulfobutoxy.

  The acylamino group includes an aliphatic acylamino group. The number of carbon atoms of the alkyl moiety in the acylamino group is preferably 1 to 4. Examples of the acylamino group include acetylamino, propionylamino, butyrylamino, isobutyrylamino and the like.

  The alkylsulfonylamino group preferably has 1 to 4 carbon atoms. Examples of the alkylsulfonylamino group include methylsulfonylamino, ethylsulfonylamino, propylsulfonylamino and the like.

  The phenyl moiety of the phenylsulfonylamino group may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, or a nitro group. Examples of the phenylsulfonylamino group include benzenesulfonylamino, chlorobenzenesulfonylamino, toluenesulfonylamino, nitrobenzenesulfonylamino and the like.

In general formula (I), R ₂ represents a hydrogen atom or a sulfonic acid group.

  In general formula (I), n represents 0 or 1. When n is 0, it means that the sulfonic acid group is not bonded to the corresponding position in the general formula (I) and a hydrogen atom is bonded instead.

  M in general formula (I) represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium each independently. Examples of the alkali metal include lithium, sodium, and potassium. Examples of organic ammonium include alkylamines having 1 to 3 carbon atoms such as methylamine and ethylamine; 1 to 4 carbon atoms such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine. The following mono-, di- or trialkanolamines can be mentioned. In the present invention, it is preferable that M in the general formula (I) is sodium.

The carboxylic acid group, sulfonic acid group, and phosphonic acid group may be free acid type (H type) or salt type. When the carboxylic acid group or the like is in a salt form (when forming a salt), alkali metal, ammonium, and organic ammonium cations can be exemplified. As the compound represented by the general formula (I), those in which R ₁ , R ₂ and R _{3 in} the general formula (I) are all sulfonic acid groups are preferable, and the counter ion is sodium in the salt form. More preferred are sulfonic acid groups.

  The content (% by mass) of the compound represented by the general formula (I) in the ink is preferably 0.1% by mass or more and 15.0% by mass or less based on the total mass of the ink. More preferably, it is at least mass% and no more than 10.0 mass%.

  Moreover, content (mass%) of the compound represented by general formula (I) is a mass ratio with respect to content (mass%) of a self-dispersion pigment, and is 0.20 times or more and 1.00 times or less. preferable. When the mass ratio is less than 0.20 times, a sufficient optical density may not be obtained in a recording medium having high ink permeability. On the other hand, if the mass ratio is more than 1.00 times, a sufficient optical density may not be obtained in a recording medium having low ink permeability. In order to obtain an image having a high optical density on a recording medium having low ink permeability, a method of increasing the pigment content can be considered. However, when the mass ratio is more than 1.00 times, the content of the compound represented by the general formula (I) increases as the pigment content increases. Therefore, in this case, the pigment is more difficult to permeate into the recording medium and tends to remain in the vicinity of the surface of the recording medium, so that the marker resistance of the image may be slightly lowered.

  The ink of the present invention may contain another dye (coloring material) other than the compound represented by the general formula (I).

(Aqueous medium)
The ink of the present invention is an aqueous ink containing at least water as an aqueous medium. In the ink of the present invention, water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent can be used. It is preferable to use deionized water (ion exchange water) as water. The content (% by mass) of water in the ink is preferably 10.0% by mass or more and 90.0% by mass or less based on the total mass of the ink.

  The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and alcohol, polyhydric alcohol, polyglycol, glycol ether, nitrogen-containing polar solvent, sulfur-containing polar solvent and the like can be used. The content (% by mass) of the water-soluble organic solvent in the ink is 5.0% by mass or more and 90.0% by mass or less, and further 10.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. It is preferable that If the content of the water-soluble organic solvent is out of the above range, a high level of ink ejection stability may not be obtained sufficiently.

(Other additives)
In addition to the above-described components, the ink of the present invention includes a surfactant, a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, and chelation as necessary Various additives such as an agent and a water-soluble resin may be contained.

(Ink physical properties)
In the present invention, the viscosity of the ink at 25 ° C. is preferably 1.0 mPa · s or more and 5.0 mPa · s or less, and more preferably 1.0 mPa · s or more and 3.5 mPa · s or less. The static surface tension of the ink at 25 ° C. is preferably 28 mN / m or more and 45 mN / m or less. Furthermore, the pH of the ink at 25 ° C. is preferably 5 or more and 9 or less.

<Ink cartridge>
The ink cartridge of the present invention includes ink and an ink storage unit that stores the ink. And the ink accommodated in this ink accommodating part is the ink of this invention demonstrated above. FIG. 1 is a cross-sectional view schematically showing an embodiment of the ink cartridge of the present invention. As shown in FIG. 1, an ink supply port 12 for supplying ink to the recording head is provided on the bottom surface of the ink cartridge. The inside of the ink cartridge is an ink storage portion for storing ink. The ink storage portion is composed of an ink storage chamber 14 and an absorber storage chamber 16, which communicate with each other via a communication port 18. The absorber housing chamber 16 communicates with the ink supply port 12. The ink storage chamber 14 stores liquid ink 20, and the absorber storage chamber 16 stores absorbers 22 and 24 that hold the ink in an impregnated state. The ink storage unit may have a form in which the entire amount of ink stored is held by an absorber without having an ink storage chamber for storing liquid ink. Further, the ink storage portion may have a form that does not have an absorber and stores the entire amount of ink in a liquid state. Further, the ink cartridge may be configured to have an ink storage portion and a recording head.

<Inkjet recording method>
The ink jet recording method of the present invention is a method of recording an image on a recording medium by discharging the ink of the present invention described above from an ink jet recording head. Examples of the method for ejecting ink include a method for imparting mechanical energy to the ink and a method for imparting thermal energy to the ink. In the present invention, it is particularly preferable to employ a system in which thermal energy is applied to the ink and ink is ejected. Other than using the ink of the present invention, the steps of the ink jet recording method may be known.

  2A and 2B are diagrams schematically showing an example of an ink jet recording apparatus used in the ink jet recording method of the present invention. FIG. 2A is a perspective view of a main part of the ink jet recording apparatus, and FIG. 2B is a perspective view of a head cartridge. It is. The ink jet recording apparatus is provided with a conveying means (not shown) for conveying the recording medium 32 and a carriage shaft 34. A head cartridge 36 can be mounted on the carriage shaft 34. The head cartridge 36 includes recording heads 38 and 40, and is configured such that an ink cartridge 42 is set. While the head cartridge 36 is conveyed along the carriage shaft 34 in the main scanning direction, ink (not shown) is ejected from the recording heads 38 and 40 toward the recording medium 32. Then, the recording medium 32 is conveyed in the sub-scanning direction by a conveying unit (not shown), whereby an image is recorded on the recording medium 32.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited at all by the following Example, unless the summary is exceeded. In addition, what is described as “parts” and “%” with respect to the component amounts is based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Preparation of pigment dispersion 1)
20 g carbon black (specific surface area 220 m ² / g, DBP oil absorption 105 mL / 100 g), 7 mmol ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid sodium salt, 20 mmol nitric acid, and 200 mL Of pure water was mixed. This mixing was performed using a Silverson mixer at room temperature (20 ° C. or higher and 25 ° C. or lower) at 6,000 rpm. After 30 minutes, 20 mmol of sodium nitrite dissolved in a small amount of water was slowly added to the mixture. By this mixing, the temperature of the mixture reached 60 ° C., and the reaction was performed in this state for 1 hour.

  Thereafter, the pH of the mixture was adjusted to 10 using an aqueous sodium hydroxide solution. After 30 minutes, 20 mL of pure water is added, diafiltration is performed using a spectrum membrane, and then sodium ions are replaced with potassium ions by an ion exchange method, so that the pigment content becomes 10.0%. Thus, a dispersion was obtained. In this way, the self-dispersed pigment having the ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid group whose counter ion is potassium is dispersed in water on the pigment particle surface. Pigment Dispersion Liquid 1 (pigment content: 10.0%) was obtained.

  The introduction amount of the functional group containing a phosphonic acid group in the obtained pigment dispersion 1 was measured by the following method. Liquid A was prepared by diluting the pigment dispersion with pure water so that the pigment content was about 0.03%. In addition, ultracentrifugation is performed on the pigment dispersion liquid at 5 ° C. under conditions of 80,000 rpm for 15 hours, and the supernatant liquid from which the self-dispersion pigment is removed is collected, and this is about 80 times with pure water. Dilution B liquid was prepared. About the obtained A liquid and B liquid, the amount of phosphorus was quantified using the ICP emission-spectral-analysis apparatus (Brand name "SPS5100", product made from SII nanotechnology). Then, the amount of the phosphonic acid group is obtained from the difference in the amount of phosphorus between the liquid A and the liquid B, and the phosphonic acid group is included by dividing by the number of phosphonic acid groups bonded to the particle surface via other atomic groups. The amount of functional group introduced was calculated. The amount of functional group introduced was 0.27 mmol / g.

(Preparation of pigment dispersion 2)
A pigment dispersion 2 was obtained in the same manner as in the pigment dispersion 1, except that the amount of the treating agent used in the pigment dispersion 1 was changed from 7 mmol to 9 mmol. The amount of functional group introduced was 0.33 mmol / g.

(Preparation of pigment dispersion 3)
A pigment dispersion 3 was obtained in the same manner as in the pigment dispersion 1, except that the amount of the treating agent used in the pigment dispersion 1 was changed from 7 mmol to 10 mmol. The amount of functional group introduced was 0.35 mmol / g.

(Preparation of pigment dispersion 4)
A pigment dispersion 4 was obtained in the same manner as in the pigment dispersion 1, except that the amount of the treating agent used in the pigment dispersion 1 was changed from 7 mmol to 1 mmol. The amount of functional group introduced was 0.10 mmol / g.

(Preparation of pigment dispersion 5)
A pigment dispersion 5 was obtained in the same manner as in the pigment dispersion 1, except that the amount of the treating agent used in the pigment dispersion 1 was changed from 7 mmol to 0.8 mmol. The amount of functional group introduced was 0.08 mmol / g.

(Preparation of pigment dispersion 6)
First, 1.5 g of 4-aminophthalic acid (treatment agent) was added to a solution prepared by dissolving 5 g of concentrated hydrochloric acid in 5.5 g of water while being cooled to 5 ° C. Next, the container containing this solution was placed in an ice bath and the solution was stirred to keep the solution constantly at 10 ° C. or lower, and 2.2 g of potassium nitrite was dissolved in 9 g of water at 5 ° C. The solution was added. This solution was further stirred for 15 minutes, and 6 g of carbon black having a specific surface area of 220 m ² / g and a DBP oil absorption of 105 mL / 100 g was added to and mixed with the stirred solution. Thereafter, the mixture was further stirred for 15 minutes, and the resulting slurry was filtered with a filter paper (trade name: Standard filter paper No. 2; manufactured by Advantech), and the particles were sufficiently cooled with water and dried in an oven at 110 ° C. And ion-exchange water was added so that pigment content might be 10.0%, and the pigment dispersion liquid 6 which disperse | distributed the pigment was obtained. In this way, Pigment Dispersion Liquid 6 in which —C ₆ H ₃ — (COOK) ₂ groups were introduced on the surface of the pigment particles was obtained.
It was 0.68 mmol / g when the introduction amount of the functional group of the pigment in the obtained pigment dispersion liquid 6 was measured. The amount of the functional group introduced is determined by first measuring the potassium ion concentration in the prepared pigment dispersion 6 using an ion meter (manufactured by DKK), and determining the pigment in the pigment dispersion 6 from the obtained potassium ion concentration value. It calculated | required by converting into the introduction amount of the functional group of.

(Preparation of pigment dispersion 7)
An oxidized carbon black obtained by oxidizing carbon black having a specific surface area of 220 m ² / g and a DBP oil absorption of 105 mL / 100 g was used. This oxidation treatment was performed by adding 100 g of carbon black to 3 L of a sodium peroxodisulfate aqueous solution having a concentration of 1.0 mol / L, a reaction temperature of 333 K, a reaction time of 10 hours, and a stirring speed of 0.12 s ⁻¹ . After completion of the reaction, the oxidized carbon black and the reaction solution were separated by filtration, and the oxidized carbon black was neutralized with a potassium hydroxide solution having a concentration of 1.0 mol / L. After neutralization, it was treated with a centrifuge (manufactured by Hitachi Koki, CR22F) under conditions of 7.5 × 10 ⁻³ s ⁻¹ and 15 minutes. Thereafter, the supernatant was separated from the remaining salt with an ultrafiltration membrane (AHP-1010, manufactured by Asahi Kasei Co., Ltd., molecular weight cut off: 50000), and then the pigment content was adjusted to 10.0%. This pigment dispersion 7 had an electric conductivity of 1.3 mS / cm and a pH of 6.0.

<Synthesis of dyes>
(Compound A)
With reference to the description of WO 2006/051850, a compound represented by the following structural formula (II) was synthesized as a free acid form. Thereafter, ion exchange was performed according to a conventional method to obtain a sodium salt type compound A.

(Compound B)
With reference to the description in JP-A-2006-63332, a compound represented by the following structural formula (III) was synthesized as a free acid type. Then, ion exchange was performed according to a conventional method to obtain a sodium salt type compound B.

(Compound C)
With reference to the description in JP-A-2006-63332, a compound represented by the following structural formula (IV) was synthesized as a free acid type. Thereafter, ion exchange was performed according to a conventional method to obtain a sodium salt type compound C.

(Compound D)
With reference to the description of International Publication No. 2012/014954, a compound represented by the following structural formula (V) was synthesized as a free acid type. Thereafter, ion exchange was performed according to a conventional method to obtain a sodium salt type compound D.

<Preparation of ink>
Each component (unit:%) shown in the upper part of Table 1 was mixed and sufficiently stirred, and then pressure filtration was performed with a polypropylene filter (manufactured by Pole) having a pore size of 2.5 μm to prepare each ink. “Surfinol 465” in Table 1 is a trade name of a nonionic surfactant manufactured by Air Products, which is an ethylene oxide adduct of acetylene glycol, and has 10 addition moles of ethylene oxide groups. In addition, “NIKKOL BL-9EX” in Table 1 is a trade name of a nonionic surfactant manufactured by Nikko Chemicals, is polyoxyethylene lauryl ether, has an HLB value of 14.5 determined by the Griffin method, an ethylene oxide group The number of moles added is 9. The lower part of Table 1 shows the self-dispersing pigment content X (%), the dye content Y (%), and the Y / X value (times) in the ink.

<Evaluation of ink>
Each obtained ink was filled in an ink cartridge, and the ink cartridge was set in an ink jet recording apparatus (trade name “PIXUS MG5430”, manufactured by Canon Inc.) equipped with a recording head that ejects ink by the action of thermal energy. In the above-described inkjet recording apparatus, a solid image recorded by applying one ink droplet having a mass per droplet of 12 ng ± 10% to a unit area of 1/1200 inch × 1/1200 inch is recorded as “recording duty is It is defined as “100%”.

(Optical density)
A solid image (2 cm × 2 cm / 1 line) having a recording duty of 100% was recorded on the following four types of recording media (plain paper).
(1) Canon brand name “PB-Paper”
(2) Steinbeis product name “Classic White”
(3) Xerox product name “Xerox 4200 Premium Multipurpose White Paper”
(4) Product name “Bright White Inkjet Paper” manufactured by Hured Packard
One day after recording, the optical density of the solid images on the four types of recording media was measured using a reflection densitometer (Macbeth, Macbeth RD-918), and the optical density was determined by the average value, maximum value, and minimum value. Evaluation was performed. The evaluation criteria are as follows. The results are shown in Table 2. In the present invention, AA and A are acceptable levels and B and C are unacceptable levels according to the following evaluation criteria.
AA: The average value was 1.35 or more, the highest value was 1.45 or more, and the lowest value was 1.20 or more.
A: The average value was 1.30 or more, the highest value was 1.40 or more, and the lowest value was 1.15 or more (however, it was evaluated as AA when corresponding to AA).
B: The average value was 1.30 or more, the highest value was less than 1.40, or the lowest value was less than 1.15.
C: The average value was less than 1.30.

(Marker resistance)
A vertical ruled line having a thickness of 1/10 inch was recorded on a recording medium (plain paper, trade name “Classic White”, manufactured by Steinbeis). One hour after recording, the obtained vertical ruled line was marked with a yellow line marker (trade name “PROPUS2”, manufactured by Mitsubishi Pencil Co., Ltd.), and it was visually confirmed whether black tailing had occurred. The evaluation criteria for marker resistance are as follows. In this evaluation, A and B were allowed to be acceptable and C was not allowed to be acceptable according to the following evaluation criteria.
A: The tailing was hardly noticeable.
B: A little tailing occurred.
C: The tailing occurred remarkably.

Claims (6)

A water-based ink jet ink containing a self-dispersing pigment and a dye,
The self-dispersing pigment is a pigment having a functional group having a structure in which an anionic group is bonded to the particle surface via another atomic group,
The water-based ink, wherein the dye contains a compound represented by the following general formula (I).

(In the general formula (I), R ₁ and R ₃ are each independently a hydrogen atom, halogen atom, cyano group, hydroxy group, carboxylic acid group, sulfonic acid group, phosphonic acid group, sulfamoyl group, N-alkyl. An aminosulfonyl group, an N-phenylaminosulfonyl group, an alkylsulfonyl group having 1 to 4 carbon atoms (which may be substituted with a hydroxy group), a nitro group, an acyl group, a ureido group, an alkyl group having 1 to 4 carbon atoms ( An optionally substituted hydroxy group or an alkoxy group having 1 to 4 carbon atoms), an alkoxy group having 1 to 4 carbon atoms (hydroxy group, an alkoxy group having 1 to 4 carbon atoms, a sulfonic acid group, or a carboxylic acid group). Optionally substituted), an acylamino group, an alkylsulfonylamino group, or a phenylsulfonylamino group (the phenyl moiety is a halogen atom, R ₂ represents a hydrogen atom or a sulfonic acid group, n represents 0 or 1, and M represents an independent group, which may be substituted with an alkyl group having 1 to 4 carbon atoms or a nitro group. Represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium)   The content (mass%) of the compound represented by the general formula (I) is 0.20 times or more and 1.00 times or less as a mass ratio with respect to the content (mass%) of the self-dispersing pigment. 2. The water-based ink according to 1. The water-based ink according to claim 1, wherein the anionic group is —PO (OM) ₂ .   The water-based ink according to claim 3, wherein an introduction amount of the functional group is 0.10 mmol / g or more and 0.33 mmol / g or less. An ink cartridge comprising ink and an ink containing portion for containing the ink,
An ink cartridge, wherein the ink is the water-based ink according to any one of claims 1 to 4. An inkjet recording method for recording an image on a recording medium by discharging ink from an inkjet recording head,
The ink-jet recording method according to claim 1, wherein the ink is the water-based ink according to claim 1.

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