JP2007063493A - Inkjet ink, method for making inkjet ink, inkjet recording method, and ink cartridge using the ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink excellent in fixability, marker resistance, rubbing resistance, character quality, controlled bleeding, etc., to provide a method for economically obtaining the ink, and to provide an inkjet recording method using the ink. <P>SOLUTION: The inkjet ink is one essentially consisting of water, a colorant, and a plurality of kinds of water-soluble organic solvents, wherein the colorant essentially consists of at least one resin-dispersed pigment capable of being dispersed in an aqueous medium with the aid of a polymer dispersant and a self-dispersible pigment composed of a pigment particle and at least one ionic group bonded to the surface of the pigment particle directly or through another atomic group, the water-soluble organic solvents are ones that undergo perfectly no or substantially no solvation, and at least one of the water-soluble organic solvents in the ink is a poor solvent for the self-dispersible pigment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet ink, a method for producing an inkjet ink, an inkjet recording method, and an ink cartridge using the ink.

  Conventionally, as inks for writing instruments (fountain pens, sign pens, water-based ballpoint pens, etc.) and ink-jet inks, pigments with high density of printed matter and images with excellent water resistance and light resistance have been used. There have been many proposals for pigmented inks. In particular, as a pigment used in an inkjet ink, a self-dispersing pigment having excellent storage stability and ejection characteristics is used, and the density and character quality on a recording medium, as well as a black image portion and a color image portion, The pigment ink contains a specific salt for the purpose of suppressing the phenomenon that the color is blurred at the boundary of the ink or the ink is mixed unevenly and the image quality is deteriorated (hereinafter referred to as “bleeding”). Has been proposed (see Patent Document 1).

  In addition, for the purpose of effectively suppressing the occurrence of blurring of the image and realizing a high quality image excellent in water resistance and scratch resistance, a self-dispersing pigment is used as a coloring material in the ink. Furthermore, it has been proposed to mix glycol ethers and water-soluble emulsions (see Patent Document 2).

  Furthermore, for the purpose of improving the fixing property of the ink, increasing the ink dot diameter, and improving the uniformity of the density within the ink dot, it is dispersed in an aqueous medium by a self-dispersing pigment as a coloring material in the ink and a polymer dispersant. There is also a proposal about using a pigment that can be made to be used (see Patent Documents 3 and 4).

JP 2000-198955 A International Publication No. 98/21284 Pamphlet JP 2001-254039 A JP 2000-239589 A

  However, in recent years, with the improvement of the ink jet technology, a higher level of recording material is required than before. In particular, as recorded materials used in offices, high density, high color development, as well as fixing, marker resistance, scratch resistance, character quality, and bleeding, which are output by a laser printer using powder toner. There is a demand for printed matter that is excellent in suppression of color. Under such circumstances, some users may not be satisfied with the level of the recorded matter output by the conventional inkjet ink.

  For example, when an image is formed on plain paper with a pigment ink that uses a pigment that can be dispersed in an aqueous medium by a polymer dispersant as a coloring material, the fixing property, marker resistance, scratch resistance, etc. May be satisfied. However, in terms of color development (high density, high color development), character quality, and suppression of bleeding, it is not possible to obtain a sufficiently satisfactory recorded material. On the other hand, when a pigment capable of self-dispersion in which at least one ionic group is bonded directly or via another atomic group to the surface of the pigment particle is used as the coloring material of the ink, An image of a satisfactory level can also be output. However, the occurrence of bleeding in the image obtained at the time of high-speed printing, and the points such as marker resistance, scratch resistance and fixability are compared with the image output by a laser printer using powder toner. Has not yet reached a satisfactory level.

  In addition, as a coloring material, a self-dispersing pigment that has been proposed conventionally is used, and further, an ink that contains a polymer compound in the ink is used. Even if an ink using both a mold pigment and a resin-dispersed pigment is used, the level of recorded matter desired by the user may not be satisfied.

  For this reason, the present inventors have developed a color development property that is slightly more than that of a conventional inkjet ink, in order to form an image that is as close as possible to an image output by a laser printer using powder toner. Recognized that it is important to improve fixing and marker resistance, scratch resistance and character quality, suppression of bleeding, and the like.

  In view of the above, the first problem to be solved by the present invention is an ink jet ink excellent in color developability, and further in fixing and marker resistance, scratch resistance, character quality, bleeding suppression, and the like. Is to provide. In addition, the second problem to be solved by the present invention is to provide an ink-jet ink that gives an image excellent in color developability, and further in fixing and marker resistance, scratch resistance, character quality, bleeding suppression and the like. Another object of the present invention is to provide a method for producing an ink-jet ink that can be obtained in a practical manner. Furthermore, the third problem to be solved by the present invention is an ink jet recording which can give an image excellent in color development, and further in fixability and marker resistance, scratch resistance, character quality, suppression of bleeding and the like. A method and ink cartridge are provided.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have arrived at the present invention. That is, the present invention is an inkjet ink comprising at least water, a color material, and a plurality of different water-soluble organic solvents, and the color material is dispersed in an aqueous medium by at least a polymer dispersant. One or more types of resin-dispersed pigments (hereinafter referred to as resin-dispersed pigments), and self-dispersed pigments in which at least one ionic group is bonded to the surface of pigment particles directly or through other atomic groups (Hereinafter referred to as self-dispersing pigment), and the self-dispersing pigment is one in which the water-soluble organic solvent is not completely or substantially solvated, and the water-soluble organic solvent in the ink. At least one of these is an ink for inkjet which is a poor solvent for the self-dispersing pigment.

  Further, a means for solving the second problem is a method for producing an inkjet ink using a plurality of inks to obtain an ink having the above composition, and at least a plurality of water-soluble organics of different types from water. A solvent and a self-dispersing pigment, and the self-dispersing pigment is one in which the water-soluble organic solvent is not completely or substantially solvated, and among the water-soluble organic solvents in the ink Having a step of injecting an inkjet ink containing at least one type of resin-dispersed pigment into an inkjet ink tank in which at least one type of inkjet ink is a poor solvent for the self-dispersing pigment. This is a method for producing an inkjet ink.

  Means for solving the third problem is an ink jet recording method and an ink jet cartridge using the ink jet ink or the ink jet ink produced by the ink jet ink producing method. .

  According to the present invention, an ink-jet ink excellent in color development on plain paper, and further in fixing and marker resistance, scratch resistance, character quality, suppression of bleeding, and the like, such an excellent ink-jet ink, By reusing the ink jet ink remaining in the ink tank, there is provided a method for producing the ink jet ink that can be obtained economically and by means preferable from the viewpoint of environmental protection. Further, there are provided an ink jet recording method and an ink cartridge capable of giving an image excellent in color developability, as well as fixability and marker resistance, scratch resistance, character quality, and bleeding suppression on plain paper.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments. In the present invention, a conventional ink-jet ink using a resin-dispersed pigment or a self-dispersing pigment as a coloring material, or an ink-jet ink containing both a resin-dispersed pigment and a self-dispersing pigment is used. Compared to the case where an image is formed, it is possible to obtain an image having improved color development on plain paper, and further improved fixability and marker resistance, scratch resistance, character quality, bleeding suppression, etc. Provide ink. As a specific means thereof, at least a resin-dispersed pigment and a self-dispersing pigment are used as a coloring material in an inkjet ink comprising at least water, a coloring material, and a plurality of different types of water-soluble organic solvents. And the self-dispersing pigment does not completely or substantially solvate with respect to the water-soluble organic solvent, and at least one of the water-soluble organic solvents in the ink is the self-dispersing pigment. An ink which is a poor solvent for the ink is used as an inkjet ink.

  The inkjet ink according to the present invention comprises a self-dispersing pigment having a relationship that does not completely or substantially solvate at least a water-soluble organic solvent contained in the ink, and the water-soluble organic solvent comprises: It is premised on comprising a poor solvent for the self-dispersing pigment. In the present invention, by using such a self-dispersing pigment as an ink coloring material, the aggregation of pigments on a recording medium is further promoted as compared with a pigment ink using a conventional self-dispersing pigment. Is possible. The present inventors presume the reason why the aggregation rate of the pigment is improved in the ink according to the present invention as compared with the pigment ink using the conventional self-dispersing pigment.

  Immediately after the ink has landed on the recording medium, the pigment in the ink starts to aggregate as the water evaporates or penetrates into the recording medium. At this time, the self-dispersing pigment used in the present invention, the water-soluble organic solvent in the ink does not completely or substantially solvate the pigment, so the dispersion stability effect due to solvation is reduced, It is considered that the aggregation of the pigments on the recording medium is caused more significantly than in the case of the conventional self-dispersing pigment.

  When the case where the above effect becomes more prominent is expressed using numbers, the ratio of the self-dispersing pigment in the ink (content in the ink) is A (mass%), and the ratio of the poor solvent in the ink (ink) It is more preferable that the ratio of B with respect to A is equal to or greater than B (mass content). Further, in order to further agglomerate the pigment in the upper layer portion of the recording medium and improve the color developability, when the total amount of the poor solvent in the ink is B and the total amount of the good solvent is C, C: B is 10 by mass ratio. : More preferably, the range is from 5 to 10:30.

Further, in the present invention, more preferable self-dispersing pigments include self-dispersing pigments in which the -R- (COOM1) _n group is bonded to the surface of the pigment particles directly or through another atomic group. It is done. R in the above formula represents an alkyl group or an aromatic ring, M1 represents a hydrogen atom, an alkali metal, ammonium or organic ammonium, and n represents an integer of 2 or more. This is because, when the -R- (COOM1) _n group as described above is bonded to the surface of the pigment particle, the effect of the water-soluble organic solvent not being solvated due to the influence of steric hindrance or the like is further promoted. This is considered to be because the aggregation of the pigments occurs more remarkably when the ink is applied to the recording medium. Furthermore, in the present invention, it is preferable to contain a salt (electrolyte) in the ink.

  Furthermore, the ink-jet ink of the present invention is characterized by containing one or more kinds of resin-dispersed pigments as a color material. In general, when a resin-dispersed pigment is contained in the ink, the pigment particles on the recording medium after the ink is applied to the recording medium are totally or locally included in the resin as the dispersant. In addition, it is possible to improve the fixing property, marker resistance, and scratch resistance of the printed matter. However, when only a resin-dispersed pigment is used as a color material, it takes time until the pigment is completely agglomerated on the recording medium. Therefore, color development and suppression of bleeding during high-speed printing are sufficiently satisfactory. May not reach level. On the other hand, as a result of the study by the present inventors, a configuration is used in which a self-dispersing pigment having a relationship that does not completely or substantially solvate with a water-soluble organic solvent is used as a coloring material together with the resin-dispersed pigment. As a result, it is possible to provide a printed matter superior in color developability, optical density, fixability and marker resistance, scratch resistance, character quality, suppression of bleeding, etc., as compared with conventional inkjet inks. I found.

  Hereinafter, the present invention will be described in more detail. The effect of forming an image using the inkjet ink according to the present invention is that the self-dispersion has a relationship that does not completely or substantially solvate with respect to the water-soluble organic solvent contained as a coloring material in the ink. It differs depending on the content ratio of the type pigment (hereinafter referred to as a self-dispersing pigment that does not solvate with the solvent) and the resin dispersed pigment. For example, the main effect when the content of the self-dispersing pigment that does not solvate with the solvent is larger than that of the resin-dispersed pigment is that the color developability is improved when an image is formed on plain paper. . As the reason why the color developability is improved by using the ink-jet ink of the present invention, the present inventors presume as follows.

  As described above, the self-dispersing pigment that does not solvate with the solvent for the water-soluble organic solvent contained in the ink-jet ink according to the present invention, Aggregates are rapidly formed due to a rapid increase in the ratio of the pigment and the poor solvent accompanying the penetration. As a result, aggregates are formed in the upper layer portion of the recording medium before the pigment is diffused over a wide range of the recording medium (see FIGS. 3A and 3B). On the other hand, the resin-dispersed pigment has a slower aggregation rate of the pigment on the recording medium than the self-dispersed pigment that does not solvate with the solvent, and thus diffuses more widely than the self-dispersed pigment. As a result, since the pigment aggregate formed by the resin dispersed pigment adheres to a portion where the amount of the pigment aggregate formed by the self-dispersing pigment that does not solvate with the solvent is relatively small, the solid uniformity is improved. It is estimated that the color development is improved as compared with the conventional inkjet ink (see FIG. 3C).

  Furthermore, as another effect, although the color developability and optical density of the formed image are substantially the same, the fixing property, the marker resistance, and the scratch resistance are significantly higher than those of the conventional ink jet ink. It is possible to improve it. The reason for this is estimated by the inventors as follows.

  When an image is formed using the ink according to the present invention, the aggregation speed of the pigments on the recording medium of the self-dispersing pigment that does not solvate with the solvent used as the coloring material is faster than the conventional self-dispersing pigment. It is possible to express the same level of color developability with a smaller applied amount than conventional ink jet inks. Furthermore, since the self-dispersing pigment that does not solvate with the solvent used in the present invention quickly aggregates on the recording medium, the resin-dispersed pigment that is contained together in the ink is also faster than sinking into the recording medium. It is present in the upper layer portion of the recording medium in an intertwined manner with the aggregate of the self-dispersing pigment. As a result, the resin-dispersed pigment is present in a form that sufficiently covers the aggregate of self-dispersing pigment that does not solvate with the solvent present in the upper layer of the recording medium. It is considered that it is possible to improve the property and scratch resistance.

  On the other hand, the main effect when the resin-dispersed pigment is more in the ink than the self-dispersed pigment that does not solvate with the solvent is as follows. As compared with the case of forming an image using an ink based on the above, it is possible to improve the character quality, the bleeding suppression effect of a color image, and the color developability. The present inventors presume the reason why suppression of bleeding and color development are improved by using the inkjet ink according to the present invention.

  When the ink of the present invention is applied to a recording medium, the resin-dispersed pigment contained in the ink starts to agglomerate as the water evaporates or permeates while spreading after the ink has landed on the recording medium. On the other hand, a self-dispersing pigment that does not solvate with a solvent forms a pigment aggregate more rapidly than the resin-dispersed pigment (see FIGS. 3D and 3E). Since this agglomerate is rapidly formed as the ratio of the poor solvent is increased, the resin dispersion is performed because it is formed as if the bank of the pigment is formed at the outer edge portion, not at the center portion of the ink dot. It becomes possible to suppress the diffusion of the pigment (see FIG. 3F). Therefore, the image formed by the ink according to the present invention has a sharper outline of the dot, and even when other ink is applied to the adjacent portion of the dot, bleeding is performed more than the conventional inkjet ink. It is possible to suppress.

  The solvation referred to in the present invention means the affinity of a pigment for a water-soluble organic solvent (medium), and depends on how much the pigment has a portion having an affinity for the medium. As an example of the part having affinity with the medium, there is a surface part of the pigment particle to which no ionic group is bonded. For example, when the group having an ionic group is bonded to the surface of the pigment particle at a high density, the exposed area of the surface portion of the pigment particle having an affinity for the medium is small and covers the surface of the pigment particle at a higher density. It is presumed that the medium becomes difficult to solvate with respect to the pigment due to a synergistic effect with the influence of steric hindrance by the ionic group.

  Hereinafter, an example of a method for determining that the water-soluble organic solvent does not completely or substantially solvate the target pigment will be described. The determination that the water-soluble organic solvent does not completely or substantially solvate the pigment can be made by measuring how much the surfactant is adsorbed to the target pigment. As described above, the degree of solvation depends on how much the pigment has a part having affinity with a medium such as a water-soluble organic solvent. It can be said that there is a correlation with the amount of adsorption. That is, in a pigment that substantially solvates with a medium such as a water-soluble organic solvent, the above-mentioned affinity portion is large or large, and the amount of adsorption of the surfactant is also large. On the other hand, in a pigment that does not completely or substantially solvate with a medium such as a water-soluble organic solvent, the above-mentioned affinity portion is small or small, and the adsorption amount of the surfactant is very small.

  Surfactant has the property that the surface tension of the liquid changes remarkably depending on its concentration, so measurement of surface tension is effective as an index for estimating how much surfactant is adsorbed to the pigment. It is considered to be a safe means. For example, when comparing the surface tension of an aqueous solution containing a certain concentration of a surfactant with the surface tension of a liquid composed of the same concentration of a surfactant, a certain concentration of pigment, and water, the surfactant is in relation to the pigment. In the case of hardly adsorbing, since the effective concentration of the surfactant that contributes to the reduction of the surface tension is almost the same in both liquids, the surface tension of the liquid is also almost the same. Conversely, when the amount of surfactant adsorbed on the pigment is large, the effective concentration of the surfactant in the liquid containing the pigment decreases, so the degree of decrease in surface tension is small compared to the surfactant aqueous solution that does not contain the pigment. Become. In other words, unless the pigment has the effect of significantly reducing the surface tension of the liquid, the surface tension of the aqueous solution containing a certain concentration of surfactant, and a liquid comprising the surfactant of the same concentration, the pigment of a certain concentration, and water. It is possible to estimate how much the surfactant is adsorbed to the pigment from the difference in surface tension.

  Specifically, first, a liquid [Liquid 1] composed of a surfactant and water and having a surfactant concentration of 2 mmol / kg, the surfactant, a pigment and water, and the surfactant concentration. Liquids [Liquid 2] having a pigment concentration of 5% by mass at 2 mmol / kg are prepared, and then the surface tension of these liquids is measured to determine as follows.

  The surfactant is not particularly limited as long as the surface tension of the liquid is remarkably changed depending on the concentration thereof, but those having the surface tension of [Liquid 1] of 50 mN / m or less are preferable. Examples of the surfactant suitably used in the above determination include those having a structure represented by the following structural formula (1), structural formula (2), or the like.

（但し、上記構造式（１）中、Ｒはアルキル基を表し、ｎは整数を表す。）

(In the structural formula (1), R represents an alkyl group, and n represents an integer.)

（但し、上記構造式（２）中、ｍ及びｎは、それぞれ整数を表わす。）

(In the structural formula (2), m and n each represent an integer.)

  When preparing the above [Liquid 2], when collecting the pigment from the ink form, remove components other than the pigment as much as possible by using ultrafiltration, centrifugation, drying under reduced pressure and high temperature environment, etc. It is preferable to keep it. If there are a lot of components other than pigments, such as solvents, surfactants, additives, etc. contained in the ink, the surface tension of the liquid will change depending on those components, or the degree of surfactant adsorption to the pigments This is because there is a possibility that an accurate determination result cannot be obtained. It is preferable that the surface tension of a liquid composed of a pigment collected from ink and water and having a pigment concentration of 5% by mass is 65 mN / m or more.

  After sufficiently stirring [Liquid 1] and [Liquid 2] produced as described above, the respective surface tensions are measured. When the surface tension of [Liquid 1] is A (mN / m) and the surface tension of [Liquid 2] is B (mN / m), a relationship of B−A ≦ 10, preferably B−A ≦ 5 is established. When satisfied, it is determined that the surfactant is not completely or substantially adsorbed to the pigment, and such a pigment does not completely or substantially solvate with a medium such as a water-soluble organic solvent. It is determined to be a pigment.

  Furthermore, the poor solvent and the good solvent described in the present invention are those in which a water-soluble organic solvent having good pigment dispersion stability is defined as a good solvent and a poor water-soluble organic solvent is defined as a poor solvent. More specifically, the particle size of the pigment in the liquid when the pigment dispersion containing about 50% by mass of the solvent to be determined and containing the pigment in a dispersed state is stored at 60 ° C. for 48 hours, The solvent to be judged does not contain the solvent or contains a small amount, and the pigment dispersion containing the pigment in a dispersed state is the same as or smaller than the pigment particle diameter. Is defined as a poor solvent.

<Inkjet ink>
Next, each component constituting the ink according to the present invention will be described, and the present invention will be described in detail.
[Color material]
As the color material constituting the ink according to the present invention, at least a resin-dispersed pigment and a self-dispersing pigment that does not solvate with a solvent are used. First, the self-dispersing pigment used in the present invention will be described.

(Self-dispersing pigment)
The self-dispersing pigment used in the present invention is characterized in that at least one ionic group is bonded to the pigment particle surface directly or through another atomic group. If there is, it will not be specifically limited. For example, a pigment in which a compound having an ionic group is bonded to the pigment particle surface by using a diazo coupling method, an ionic group is introduced to the pigment particle surface by surface oxidation treatment such as sodium hypochlorite or ozone treatment in water. A pigment or the like can be used. These pigments can be used alone or in combination of two or more.

In particular, by using a diazo coupling method,-(COOM1) _n , -SO ₃ M1 and -PO ₃ H (M1) ₂ (M1 in these formulas represents a hydrogen atom, an alkali metal, ammonium or organic ammonium). , N represents an integer of 1 or more), and a pigment chemically bonded to the pigment particle surface directly or via other atomic groups can be preferably used. Furthermore, it is preferable that the other atomic group is an alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted naphthylene group. Among the ionic groups, when the — (COOM1) _n group is bonded to the surface of the pigment particle at a higher density, the promotion of solid-liquid separation caused by the degree of solvation described above occurs more significantly. The effect of the present invention can be obtained more clearly.

More specifically, in the present invention, a self-dispersing pigment in which the —R— (COOM1) _n group is bonded to the surface of the pigment particle directly or through another atomic group is more preferable. . R in the above formula represents an alkyl group or an aromatic ring, M1 represents a hydrogen atom, an alkali metal, ammonium or organic ammonium, and n represents an integer of 2 or more. Among these, particularly when a pigment having a structure in which a —C ₆ H ₃ — (COOM1) ₂ group is introduced is used, the preferable effect of the present invention is exhibited.

Regarding the introduction amount of the ionic group such as the -C ₆ H _3- (COOM1) ₂ group to the surface of the pigment particle, it is preferable that the introduction amount per unit surface area of the pigment particle is larger in the configuration of the present invention. Is demonstrated. As described above, this is considered to be because the degree of solvation of the water-soluble organic solvent with respect to the pigment decreases due to steric hindrance or the like as the ionic group increases.

(Resin dispersion pigment)
In the ink according to the present invention, a resin-dispersed pigment that can be dispersed by a polymer dispersant is used together with the above-described self-dispersing pigment. In the case of the pigment, unlike the above self-dispersing pigment, a compound for dispersing the hydrophobic pigment is required. Examples of such a material include so-called dispersants, surfactants, resin dispersants (polymer dispersants), and the like. In the present invention, a polymer dispersant (resin dispersant) is used for the reason described above. Resin dispersants include styrene and its derivatives, vinyl naphthalene and its derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid and its derivatives, maleic acid and its derivatives, itaconic acid and its A block copolymer comprising at least two monomers (of which at least one is a hydrophilic monomer) selected from derivatives, fumaric acid and derivatives thereof, vinyl acetate, vinyl alcohol, vinyl pyrrolidone, acrylamide, and derivatives thereof. Examples thereof include a polymer, a random copolymer, a graft copolymer, and salts thereof.

  Moreover, you may use together a dispersing agent or surfactant as listed below with a polymer dispersing agent. For example, anionic and nonionic ones can be suitably used. Examples of the anionic compounds include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensates, polyoxyethylene alkyls. Sulfuric acid ester salts, substituted derivatives thereof, etc .; nonionic compounds include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, Examples thereof include polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethyleneoxypropylene block polymer, and substituted derivatives thereof.

(Pigment)
The ink according to the present invention includes the above-described resin-dispersed pigment and a self-dispersed pigment whose surface of the pigment particle is modified, which differ in the method of dispersing in an aqueous medium. The pigment particles that can be used are not particularly limited, and any of those listed below can be used.

  Carbon black is suitable as the pigment used in the black ink. For example, carbon black such as furnace black, lamp black, acetylene black and channel black can be used. Specifically, for example, Raven 7000, Ray Van 5750, Ray Van 5250, Ray Van 5000 ULTRA, Ray Van 3500, Ray Van 2000, Ray Van 1500, Ray Van 1250, Ray Van 1200, Ray Van 1190 ULTRA-II, Ray Van 1170, Ray Van 1255 (above, Colombia), Black Pearls L, Regal 400R, Regal 330R, Legal 660R, Mogul L, Monarch 700, Monak 800, Monak 880, Monak 900, Monak 1000, Monak 1100 Monak 1300, Monak 1400, Monak 2000, Vulcan XC-72R (above, Cabo Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (above, manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. Commercial products such as 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical) can be used.

  Carbon black newly prepared for the present invention can also be used. However, the present invention is not limited to these, and any conventionally known carbon black can be used. Further, the material is not limited to carbon black, and magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used as the black pigment.

  Examples of pigment particles used other than black ink include various organic pigment particles. Specific examples of the organic pigment include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, and pyrazolone red, and soluble azo pigments such as ritole red, heliobordeaux, pigment scarlet, and permanent red 2B. Derivatives from vat dyes such as alizarin, indanthrone, thioindigo maroon, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, quinacridone pigments such as quinacridone red and quinacridone magenta, and perylene pigments such as perylene red and perylene scarlet , Isoindolinone yellow, isoindolinone pigments such as isoindolinone orange, benzimidazolone yellow, benzimidazolone orange, benzimidazolone red Imidazolone pigments, pyranthrone pigments such as pyranthrone red, pyranthrone orange, indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel Azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and the like can be mentioned. Of course, it is not limited to these, Other organic pigments may be used.

  Moreover, the organic pigment that can be used in the present invention is represented by the color index (CI) number, and examples thereof include the following.

C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153, 154, 166, 168, 180, 185 etc.

C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71 etc.

C. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272 etc.

C. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50, etc.

C. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, etc.

C. I. Pigment Green 7, 36 etc. C.I. I. Pigment Brown 23, 25, 26, etc.

  In the ink according to the present invention, the content of the pigment described above is preferably 0.1 to 15% by mass, particularly preferably 1 to 10% by mass, based on the total mass of the ink.

(Water-soluble organic solvents and additives)
The ink according to the present invention contains water and a plurality of different water-soluble organic solvents as an aqueous medium. Furthermore, in the present invention, it is required that at least one of the water-soluble organic solvents in the ink is a poor solvent for the self-dispersing pigment. Therefore, regarding the plurality of water-soluble organic solvents constituting the ink according to the present invention, the water-soluble organic solvent to be used is a good solvent and a poor solvent for the self-dispersing pigment used in the ink according to the determination method described later. And at least one of them is a poor solvent. Further, when the content of the self-dispersing pigment in the ink-jet ink according to the present invention is A (mass%) and the content of the poor solvent is B (mass%), the ratio of B to A is equal to or more than. It is preferable.

  Examples of the water-soluble organic solvent that can be used in the present invention include C1-C4 alkanols such as ethanol, isopropanol, n-butanol, isobutanol, secondary butanol, and tertiary butanol, N, N-dimethylformamide, or N , Carboxylic acid amides such as N-dimethylacetamide, acetone, methyl ethyl ketone, ketones such as 2-methyl-2-hydroxypentan-4-one, or cyclic ethers such as ketoalcohol, tetrahydrofuran, dioxane, glycerin, ethylene glycol, diethylene glycol , Triethylene glycol, tetraethylene glycol, 1,2- or 1,3-propylene glycol, 1,2- or 1,4-butylene glycol, polyethylene glycol, 1,3-butanediol, 1,5-penta Diol, 1,2-hexanediol, 1,6-hexanediol, dithioglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol, acetylene glycol derivative, trimethylolpropane, etc. Polyhydric alcohols, alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether, 2-pyrrolidone, N-methyl- Preferable examples include 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-methylmorpholine, sulfur-containing compounds such as dimethyl sulfoxide, urea, urea derivatives, and the like.

  In addition to this, the ink according to the present invention includes a surfactant, a pH adjuster, a chelating agent, a rust inhibitor, an antiseptic, an antifungal agent, an ultraviolet absorber, a viscosity modifier, an antifoaming agent, and Various additives such as a water-soluble polymer may be contained.

  As the surfactant, for example, anionic surfactants, amphoteric surfactants, cationic surfactants, nonionic surfactants and the like as listed below can be used. Examples of the anionic surfactant include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acyl amino acids and salts thereof, N-acyl methyl taurate, alkyl sulfate polyoxy Alkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester, lauryl alcohol sulfate ester, alkylphenol type phosphate ester, alkyl type phosphate ester, alkylallylsulfone hydrochloride, diethylsulfone Acid salts, diethylhexyl sulfosuccinate dioctyl sulfosuccinate and the like.

  Examples of the cationic surfactant include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives. Amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine, and other imidazoline derivatives. Etc.

  Nonionic surfactants include, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, polyoxyethylene Ether type such as allylalkyl alkyl ether, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene Ester type such as monooleate, polyoxyethylene stearate, 2,4,7,9-tetramethyl-5-decyne-4,7 Acetylene glycols such as diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol (for example, acetylenol EH manufactured by Kawaken Fine Chemicals, manufactured by Nisshin Chemical) Surfinol 104, 82, 465, Olphine STG, etc.).

  As the pH adjusting agent, any substance can be used as long as it can control the pH of the ink within a predetermined range. For example, alcohol amine compounds such as diethanolamine, triethanolamine, isopropanolamine, trishydroxymethylaminomethane, alkali metal hydroxides such as lithium hydroxide and potassium hydroxide, ammonium hydroxide, or lithium carbonate, sodium carbonate, carbonate Examples thereof include alkali metal carbonates such as potassium.

  Examples of antiseptics and antifungal agents include organic sulfur, organic nitrogen sulfur, organic halogen, haloallylsulfone, iodopropargyl, N-haloalkylthio, benzthiazole, nitrityl, pyridine, 8-oxyquinoline, benzothiazole, isothiazoline, dithiol, pyridine oxide, nitropropane, organotin, phenol, quaternary ammonium salt, triazine, thiadiazine, anilide, adamantane, dithio Examples thereof include carbamate compounds, brominated indanone compounds, benzyl bromacetate compounds, and inorganic salt compounds.

  Examples of the organic halogen compound include sodium pentachlorophenol, examples of the pyridine oxide compound include sodium 2-pyridinethiol-1-oxide, and examples of the inorganic salt compound include acetic anhydride. Examples of the isothiazoline compound include 1,2-benzisothiazoline-3-one, 2-n-octyl-4-isothiazoline-3-one, and 5-chloro-2-methyl-4-isothiazoline-3. -One, 5-chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride and the like. Other antiseptic / antifungal agents include sodium sorbate sodium benzoate and the like, for example, Avecia Proxel GXL (S), Proxel XL-2 (S) and the like.

  Examples of the chelating agent include sodium citrate, sodium ethylenediaminetetraacetate, sodium 2nitrotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate and the like.

  Examples of the rust preventive include acidic sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol nitrate, dicyclohexylammonium nitrite and the like.

  As the ultraviolet absorber, for example, a benzophenone compound, a benzotriazole compound, a cinnamic acid compound, a triazine compound, a stilbene compound, or a compound that emits fluorescence by absorbing ultraviolet rays typified by a benzoxazole compound, So-called fluorescent brighteners can also be used.

  Examples of the viscosity modifier include water-soluble polymer compounds in addition to water-soluble organic solvents, and examples thereof include polyvinyl alcohol, cellulose derivatives, polyamines, and polyimines. As the antifoaming agent, a fluorine-based or silicone-based compound can be used as necessary.

<Method for creating ink-jet ink>
The ink-jet ink according to the present invention contains one or more kinds of resin-dispersed pigments and self-dispersing pigments, which are the essential constituents and constituent requirements described above, The water-soluble organic solvent does not completely or substantially solvate, and at least one of the water-soluble organic solvents in the ink may be a poor solvent for the self-dispersing pigment, The manufacturing method is not particularly limited.

  The ink according to the present invention can be easily produced according to a conventional method in the case of producing an inkjet ink using the above-described component materials. As another method, by reusing the ink jet ink remaining in the ink tank, which will be described below, the ink jet ink according to the present invention can be obtained by means which are economical and preferable from the viewpoint of environmental protection. Can be created.

  That is, a method for producing an inkjet ink using a plurality of inks to obtain an ink having the composition described above, comprising at least water, a plurality of different types of water-soluble organic solvents, and a self-dispersing pigment. The self-dispersing pigment is one in which the water-soluble organic solvent is not completely or substantially solvated, and at least one of the water-soluble organic solvents in the ink is based on the self-dispersing pigment. A step of injecting an ink-jet ink containing one or more kinds of resin-dispersed pigments, which can be dispersed in an aqueous medium by a polymer dispersant, into an ink-jet ink tank containing an ink-jet ink that is a poor solvent. Examples thereof include a method for producing an ink-jet ink characterized by having the ink. According to the above-described method, it is possible to reuse the ink tank or the ink cartridge containing the specific self-dispersing pigment and the poor solvent for the self-dispersing pigment, and the cost can be reduced. Further, by adopting the above-described ink production method, in ink production, an ink tank having an ink once contained therein and an ink cartridge having an ink containing portion for containing the ink are easily filled with ink. An incidental effect can also be added.

<Inkjet recording method>
The ink jet ink according to the present invention can be preferably used in an ink jet recording method in which ink is ejected from an orifice in accordance with a recording signal to perform recording on a recording medium. In particular, it can be preferably used in an ink jet recording method in which thermal energy is applied to ink to perform recording on a recording medium.

"ink cartridge"
As an ink cartridge suitable for performing recording using the ink-jet ink according to the present invention, an ink cartridge having an ink containing portion for containing these inks can be mentioned. Specific examples of ink cartridges suitable for recording using the ink jet ink according to the present invention are shown below.

  FIG. 1 is a schematic explanatory view and a sectional view of a liquid storage container which is an ink cartridge suitable for performing recording using the ink-jet ink of the present invention. In FIG. 1, the liquid storage container (ink tank) is connected to the atmosphere via the atmosphere communication port 112 at the upper part, communicates with the ink supply port at the lower part, and stores a negative pressure generation member storage chamber 134 that stores the negative pressure generation member therein. And a substantially sealed liquid storage chamber 136 for storing liquid ink by a partition wall 138. The negative pressure generating member storage chamber 134 and the liquid storage chamber 136 are near the bottom of the liquid storage container, and facilitate the introduction of the atmosphere into the liquid storage chamber during the liquid supply operation with the communication hole 140 formed in the partition wall 138. For this purpose, the air is communicated only through an air introduction groove (atmosphere introduction path) 150. A plurality of ribs are integrally formed on the upper wall of the liquid container (ink tank) that defines the negative pressure generating member storage chamber 134 so as to protrude into the inside, and is compressed into the negative pressure generating member storage chamber 134. Is in contact with the negative pressure generating member accommodated in. By this rib, an air buffer chamber is formed between the upper wall and the upper surface of the negative pressure generating member.

  The ink supply cylinder provided with the liquid supply port 114 is provided with a pressure contact body 146 having a higher capillary force and a higher physical strength than the negative pressure generating member, and is in pressure contact with the negative pressure generating member. In the illustrated negative pressure generating member storage chamber, two capillary force generating types of the first negative pressure generating member 132B and the second negative pressure generating member 132A made of olefin resin fibers such as polyethylene are used as the negative pressure generating member. The negative pressure generating member is accommodated. 132C is a boundary layer of the two negative pressure generating members, and an intersection portion of the boundary layer 132C with the partition wall 138 is an air introduction groove (atmosphere introduction) in a posture when the liquid storage container is used with the communication portion downward. Road) is present above the upper end of 150. Further, the ink accommodated in the negative pressure generating member exists above the boundary layer 132C as indicated by the ink level L.

  Here, the boundary layer between the first negative pressure generating member and the second negative pressure generating member is in pressure contact, and the vicinity of the boundary layer of the negative pressure generating member has a higher compressibility than other parts, and the capillary force Is in a strong state. That is, assuming that the capillary force of the first negative pressure generating member is P1, the capillary force of the second negative pressure generating member is P2, and the capillary force of the interface between the negative pressure generating members is PS, P2 <P1 <PS. It has become.

  FIG. 2 is a schematic explanatory view and a cross-sectional view of a liquid storage container, which is still another ink cartridge, suitable for performing recording using the ink according to the present invention. The ink cartridge includes a container 41 that stores ink of three colors, yellow (Y), magenta (M), and cyan (C), and a lid member 42 that covers the container 41.

  The interior of the container 41 is partitioned into three spaces having substantially the same capacity by two partition plates 411 and 412 arranged in parallel to each other in order to accommodate three colors of ink. These three spaces are arranged along the insertion direction of the color ink tank when the color ink tank is attached to the ink tank holder. In each of these spaces, an ink absorber 44Y that absorbs and holds yellow ink, an ink absorber 44M that absorbs and holds magenta ink, and an ink absorber 44C that absorbs and holds cyan ink. Is stored. Further, the ink stored in the ink absorber 44Y, the ink absorber 44M, and the ink absorber 44C, which are negative pressure generating members, reaches the top of each ink absorber as indicated by the ink level L. Existing.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely using an Example and a comparative example, this invention is not limited by the following Example, unless the summary is exceeded. In the following description, “parts” and “%” are based on mass unless otherwise specified. Each ink was adjusted with water to make the whole 100%. The remaining amount is the remaining amount (%) obtained by subtracting the amount (%) of each component other than the component.

(Preparation of pigment aqueous dispersion A)
First, 1.5 g of 4-aminophthalic acid is added to a solution obtained by dissolving 5 g of concentrated hydrochloric acid in 5.5 g of water while being cooled to 5 g. Next, the solution containing the solution is placed in an ice bath and the solution is stirred to keep the solution at 10 ° C. or lower, and 1.8 g of sodium nitrite is dissolved in 9 g of water at 5 ° C. Add the solution. After stirring this solution for another 15 minutes, 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 is added and mixed in the stirred solution. Then stir for another 15 minutes. Next, the obtained slurry was Toyo Filter Paper No. 2 (manufactured by Advantis), the particles were sufficiently cooled with water, and dried in an oven at 110 ° C. to prepare self-dispersing pigment A.

Further, water was added to the self-dispersing pigment A obtained above to adjust the concentration of the dispersion so that the pigment concentration was 10%. By the above method, pigment aqueous dispersion A was obtained in which self-dispersing carbon black having —C ₆ H ₃ — (COONa) ₂ groups introduced on the surface of carbon black particles was dispersed in water. When the ionic group density of the self-dispersing pigment A produced above was measured, it was 3.1 μmol / m ² . The measuring method of the ionic group density used at this time is as follows. First, the sodium ion concentration in the pigment dispersion A prepared above was measured using an ion meter (manufactured by DKK). And the ionic group density of the self-dispersing pigment A was converted from the obtained value.

(Preparation of pigment aqueous dispersion B)
First, 0.7 g of 4-aminophthalic acid is added to a solution obtained by dissolving 2.5 g of concentrated hydrochloric acid in 5.5 g of water while being cooled to 5 g. Next, the solution containing the solution is placed in an ice bath and the solution is stirred so that the solution is always kept at 10 ° C. or lower, and 0.9 g of sodium nitrite is dissolved in 9 g of water at 5 ° C. Add the solution. After stirring this solution for another 15 minutes, 10 g of carbon black having a specific surface area of 220 m ² / g and a DBP oil absorption of 105 mL / 100 g is added and mixed into the stirred solution. Then stir for another 15 minutes. Next, the obtained slurry was Toyo Filter Paper No. 2 (manufactured by Advantis), the particles were sufficiently cooled with water, and dried in an oven at 110 ° C. to prepare self-dispersing pigment B.

Further, water was added to the self-dispersing pigment B obtained above to adjust the concentration of the dispersion so that the pigment concentration was 10%. By the above method, Pigment Water Dispersion B in which self-dispersing carbon black having —C ₆ H ₃ — (COONa) ₂ groups introduced on the surface of carbon black particles was dispersed in water was obtained. When the ionic group density of the self-dispersing pigment B produced above was measured by the same method as that performed for the self-dispersing pigment A, it was 1.4 μmol / m ² .

(Preparation of pigment aqueous dispersion C)
10 parts of carbon black having a specific surface area of 210 m ² / g and a DBP oil absorption of 74 mL / 100 g, an acid value of 100, a weight average molecular weight of 5,000, and a polydispersity Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) ) 20 parts of a 10% sodium hydroxide neutralized aqueous solution of 2.2 styrene-acrylic acid copolymer and 70 parts of ion-exchanged water were mixed and dispersed for 1 hour using a sand grinder. Thereafter, coarse particles were removed by centrifugal separation treatment, and pressure filtration was performed with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare resin dispersed pigment C. Furthermore, water was added to the resin dispersion pigment C obtained above to disperse the pigment so that the pigment concentration would be 10%, thereby preparing a pigment aqueous dispersion C.

(Determination method that water-soluble organic solvent does not completely or substantially solvate the pigment)
It was determined by the method described below that the water-soluble organic solvent did not completely or substantially solvate the self-dispersing pigments A and B obtained above. Specifically, first, a liquid [liquid 1] comprising a surfactant having the following structural formula (1) or structural formula (2) and water, and having a surfactant concentration of 2 mmol / kg, and the surfactant A liquid (Liquid 2) consisting of a pigment (self-dispersing pigment A or B) and water, having a surfactant concentration of 2 mmol / kg and a pigment concentration of 5% was prepared. Liquids 1 and 2 were prepared by mixing the components and stirring for about 30 minutes at room temperature.

（但し、上記構造式（１）中、Ｒはアルキル基を表し、ｎは整数を表す。）

(In the structural formula (1), R represents an alkyl group, and n represents an integer.)

（但し、上記構造式（２）中、ｍ及びｎは、それぞれ整数を表わす。）

(In the structural formula (2), m and n each represent an integer.)

  For the self-dispersing pigments A and B obtained as described above, the surface tension at room temperature of a liquid having a pigment concentration in water of 5% was measured. As a result, it was confirmed that both were equivalent to the surface tension (72 mN / m) of water at room temperature, and that the self-dispersing pigments A and B themselves had no effect of reducing the surface tension of the liquid. Table 1 shows the measurement results of the surface tension of [Liquid 1] and [Liquid 2] described above at room temperature, and the difference in surface tension between [Liquid 2] and [Liquid 1].

  As is apparent from the results of Table 1 above, in the self-dispersing pigment A, the difference (B−A) between the surface tension B of [Liquid 2] and the surface tension A of [Liquid 1] is self-dispersing pigment. Compared to the case of B, a small value was shown. This means that in the self-dispersing pigment A, the effective concentration of the surfactant that contributes to the reduction of the surface tension of the liquid is substantially equal regardless of the presence or absence of the color material. That is, it is determined that the surfactant is not completely or substantially adsorbed with respect to the self-dispersing pigment A, and for the reason described above, the self-dispersing pigment A is completely separated from a medium such as a water-soluble organic solvent. Or a pigment that does not substantially solvate.

(Determination method of the good and poor solvents of the water-soluble organic solvent used)
In order to determine the good and poor solvents for the self-dispersing pigments A and B and the resin-dispersed pigment C, the following experiment was conducted. First, using a pigment aqueous dispersion in which these pigments are dispersed at a concentration of 10%, a dispersion for determining good and poor solvents was prepared at the following blending ratio.

[Combination ratio of dispersion for determining good and poor solvents]
-50 parts of a 10% aqueous pigment dispersion of each pigment-50 parts of each water-soluble organic solvent listed in Table 2

(Judgment method)
Next, 10 g of the good solvent / poor solvent determination dispersion prepared as described above was placed in a transparent glass lid-equipped sample bottle, capped, and then sufficiently stirred, and placed in an oven at 60 ° C. Allowed to stand for 48 hours. Then, using the dispersion liquid taken out from the oven at 60 ° C. as a measurement sample, the particle diameters of the self-dispersion pigments A and B and the resin dispersion pigment C in the liquid were measured using a concentrated particle size analyzer (trade name: FPAR-1000 ; Otsuka Electronics Co., Ltd.), measured at 60 ° C. for 48 hours and stored for 48 hours as a stock solution particle size of the dispersion for determination of good solvent and poor solvent (without dilution) Particle diameter).

  On the other hand, as a reference, the above-mentioned good solvent and poor solvent judgment dispersion liquid and pigment water dispersion with the same pigment concentration, that is, judgment comparison of good solvent and poor solvent with the same amount of water added instead of water-soluble organic solvent An aqueous pigment dispersion was prepared. Then, the water dispersion was measured for the stock solution particle size of the pigment in the liquid with a concentrated particle size analyzer without performing warming storage, and this was determined as the stock solution particle size of the reference aqueous dispersion. did.

  And the stock solution particle size of the dispersion liquid for determination of the good solvent and the poor solvent after warming storage at 60 ° C. and 48 hours previously measured was compared with the stock solution particle size of the reference aqueous dispersion. And about the thing whose stock solution particle size of the said dispersion liquid for determination is larger than the stock solution particle diameter of the reference | standard aqueous dispersion liquid, the water-soluble organic solvent is determined to be a poor solvent, When the stock solution particle size was the same as or smaller than that of the reference aqueous dispersion, the water-soluble organic solvent was judged as a good solvent.

[judgment result]
Whether the four water-soluble organic solvents shown in Table 2 that can be used in the ink as described above are poor solvents or good solvents for the self-dispersing pigment A or B or the resin-dispersed pigment C Judgment was made. The results are shown in Table 2.
○: good solvent ×: poor solvent

<< Examples 1-7 and Comparative Examples 1-4 >>
<Preparation of each ink>
Tables 3 and 4 show the water-soluble organic solvents that are determined to be poor or good solvents for the self-dispersing pigment A or B or the resin-dispersed pigment C as described above. Inks of Examples 1 to 7 and Comparative Examples 1 to 4 having the respective formulations were prepared. Each ink was prepared by mixing each component of each formulation shown in Tables 3 and 4 and then pressure-filtering with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm.

<Evaluation of each ink (print density, character quality and bleeding suppression)>
A thermal ink jet printer (trade name: PIXUS 860i; manufactured by Canon) that discharges ink droplets by applying thermal energy to the inks using the inks of Examples 1 to 7 and Comparative Examples 1 to 4 and the yellow ink shown below. ) To form an image. At that time, the following evaluation images were created using the ink tanks in which the inks described above were filled in the ink tanks of FIG. Note that the default mode shown below was selected as the print mode. Further, five types of plain papers A to E described below were used as evaluation papers. And about the following evaluation item, it evaluated according to the following evaluation method and evaluation criteria, and the obtained result was shown in Table 5.

(Print mode)
Paper type: Plain paper Print quality: Standard Color adjustment: Automatic

(Plain paper for copying)
A: Canon, PPC paper NSK
B: Canon PPC paper NDK
C: Xerox PPC paper 4024
D: Made by Fox River, PPC paper prober bond E: Made by Neuzidora, PPC paper for Canon

[Evaluation image and evaluation method for printing density]
Character printing including a solid portion of 2 cm × 2 cm was performed on the plain papers A to E for copying with each ink, and the print density of the solid portion of 2 cm × 2 cm after one day of printing was measured. The discharge amount per dot of ink is within 30 ng ± 10%. The print density of each image was measured using a reflection densitometer (trade name: Macbeth RD-918; manufactured by Macbeth).

[Evaluation image and evaluation method for character quality]
Characters of several font sizes were printed on plain papers A to E for copying, and the bleeding of the characters at that time was evaluated visually. The discharge amount per dot of ink is within 30 ng ± 10%.

[Evaluation image and evaluation criteria for bleeding suppression effect]
As a combination in which bleeding is most noticeable, an image was formed using each of the black inks of Examples and Comparative Examples and a yellow ink having the following formulation, and the occurrence of bleeding was evaluated. As the evaluation images, black ink and yellow ink were used, and solid images of 2 cm × 2 cm were respectively printed adjacently. In this case, the ejection amount per dot of ink is within 30 ng ± 10% for black ink and within 5 ng ± 10% for yellow ink. Then, the degree of occurrence of bleeding in the adjacent portion of each image by the black and yellow inks immediately after printing was visually observed. The yellow ink color material used for the evaluation includes C.I. I. Although direct yellow 86 was used, it is of course not limited to the dye, and the same applies to the case of using a yellow ink containing a general dye or pigment that is commercially available. The result can be obtained.

[Prescription of yellow ink]
・ C. I. Direct Yellow 86 3%
・ Glycerin 5%
・ Diethylene glycol 5%
・ Surfinol 465 1%
・ Remaining amount of water

〔Evaluation criteria〕
(Double-circle): Compared with the image formed with the ink of Comparative Examples 1-4, the printing density, the character quality, and the suppression of bleeding are clearly improved, and neither deterioration occurs.
◯: Compared with the images formed with the inks of Comparative Examples 1 to 4, it was confirmed that there was an improvement in at least two items of print density, character quality, and bleeding suppression, and neither deterioration occurred. .
(Triangle | delta): Compared with the image formed with the ink of Comparative Examples 1-4, it was confirmed that it improved in any one item of printing density, character quality, and suppression of bleeding, and neither deterioration also arises.
X: Compared with images formed with the inks of Comparative Examples 1 to 4, there is no difference in improvement in printing density and character quality and suppression of bleeding.

<< Examples 8 to 10 and Comparative Examples 5 to 10 >>
<Preparation of each ink>
A water-soluble organic solvent that has previously been determined whether it is a poor solvent or a good solvent for the self-dispersing pigment A or B or the resin-dispersed pigment C, and the self-dispersing pigment A or B, or the resin-dispersed pigment C Inks of Examples 8 to 10 and Comparative Examples 5 to 10 having the respective formulations shown in Tables 6 and 7 were prepared. Each ink was prepared by mixing each component of each formulation shown in Tables 6 and 7 and then pressure filtering with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm.

  Each of the inks of Examples 8 to 10 and Comparative Examples 5 to 10 having the compositions shown in Tables 6 and 7 prepared above was filled in the ink tank having the structure shown in FIG. 1 to form an image. At that time, an image was formed by the same method as in the case of using the inks of Examples 1 to 7 and Comparative Examples 1 to 4 described above, and the print density of the image formed with the ink of the example was compared with the ink of the comparative example. In comparison with the formed image, the following criteria were evaluated. The evaluation results obtained are shown in Table 8.

(Evaluation criteria)
A: Compared with images formed with the inks of Comparative Examples 5 to 10, the print density was clearly improved in all the evaluation papers.
Δ: Compared with images formed with the inks of Comparative Examples 5 to 10, the print density was improved in some evaluation papers.
X: There is no difference in print density in all the evaluation papers as compared with images formed with the inks of Comparative Examples 5 to 10.

<< Creation of Inks of Examples 11-14 >>
(Preparation of black ink 1)
The compositions shown in Table 9 were mixed and pressure filtered through a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare inkjet black ink 1 by a conventional method. The black ink 1 contains the above-described self-dispersing pigment A, and the self-dispersing pigment A is one in which a water-soluble organic solvent is not completely or substantially solvated, and is further water-soluble organic. One type of solvent is an inkjet ink, which is a poor solvent for the self-dispersing pigment A.

  14.5 g of the black ink 1 prepared according to the formulation shown in Table 9 was injected into the ink tank shown in FIG. 1, and then 12.5 g was discharged. Thereafter, 10.0 g of each of the inks of Comparative Examples 1 to 4 prepared above was injected to prepare inks of Examples 11 to 14. In addition, when these inks were extracted and the composition was analyzed, it was as shown in Table 10 below.

(Evaluation of printing density, character quality and bleeding)
The ink was evaluated in exactly the same way as the evaluation of the printing density, character quality and bleeding performed in Examples 1 to 7 and Comparative Examples 1 to 4. The evaluation results are shown in Table 11 below.

It is a schematic explanatory drawing of the liquid storage container which is an ink cartridge suitable for recording using the ink of this invention. It is a schematic explanatory drawing of the liquid storage container which is an ink cartridge suitable for recording using the ink of this invention. FIG. 3 is a schematic explanatory diagram from when ink is applied to a recording medium until fixing.

Explanation of symbols

41: Container 42: Lid members 43Y, 43M, 43C: Ink supply ports 44Y, 44M, 44C: Ink absorbers 45Y, 45M, 45C: Ink supply member 46: Retaining claw 47: Latch lever 47c: Base slope 48: Latch Claw 49: Stepped portion 112: Atmospheric communication port 114: Liquid supply port 132A: Second negative pressure generating member 132B: First negative pressure generating member 132C: First negative pressure generating member and second negative pressure generating member Boundary layer 134: negative pressure generating member storage chamber 136: liquid storage chamber 138: partition wall 140: communication hole 146: pressure contact body 150: atmosphere introduction groove (atmosphere introduction path)
411, 412: partition plate L: liquid-gas interface 1300: recording medium 1301: self-dispersing pigment 1302 used in the present invention: resin dispersed pigment 1303: aggregate of self-dispersing pigment used in the present invention

Claims (12)

  An inkjet ink comprising at least water, a coloring material, and a plurality of different types of water-soluble organic solvents, wherein the coloring material can be dispersed in an aqueous medium by at least a polymer dispersant. And a self-dispersing pigment in which at least one ionic group is bonded to the surface of the pigment particle directly or through another atomic group, and the self-dispersing pigment contains the above water-soluble pigment. The organic solvent is one that does not completely or substantially solvate, and at least one of the water-soluble organic solvents in the ink is a poor solvent for the self-dispersing pigment. ink.   2. The ratio of B to A is equal to or greater than A when the content of the self-dispersing pigment in the ink is A (mass%) and the content of the poor solvent in the ink is B (mass%). The ink for inkjet described in 2.   The inkjet ink according to claim 1, wherein the poor solvent for the self-dispersing pigment is also a poor solvent for the resin-dispersed pigment. The self-dispersing pigment is a self-dispersing pigment in which a -R- (COOM1) _n group is bonded to the surface of pigment particles directly or through another atomic group. (In the above formula, R represents an alkyl group or an aromatic ring, M1 represents any of a hydrogen atom, an alkali metal, ammonium, or organic ammonium, and n represents an integer of 2 or more.) ).   The inkjet ink according to any one of claims 1 to 4, wherein the pigment particles are carbon black.   A method for producing an ink-jet ink for obtaining an ink having the composition according to claim 1 using a plurality of inks, wherein at least water, a plurality of different water-soluble organic solvents, and at least on the surface of pigment particles A self-dispersing pigment in which one ionic group is bonded directly or through another atomic group, and the water-soluble organic solvent is not completely or substantially solvated by the self-dispersing pigment. And at least one polymer in an ink-jet ink tank containing an ink-jet ink in which at least one of the water-soluble organic solvents in the ink is a poor solvent for the self-dispersing pigment It has the process of inject | pouring the inkjet ink containing the resin dispersion pigment which can be disperse | distributed to an aqueous medium with a dispersing agent, It is characterized by the above-mentioned. How to create ink-jet ink. The inkjet ink according to claim 6, wherein the self-dispersing pigment is a self-dispersing pigment in which a -R- (COOM1) _n group is bonded to the surface of pigment particles directly or through another atomic group. (R in the above formula represents an alkyl group or an aromatic ring, M1 represents any of a hydrogen atom, an alkali metal, ammonium, or organic ammonium, and n represents an integer of 2 or more).   The method for producing an ink-jet ink according to claim 6 or 7, wherein the pigment particles are carbon black.   An inkjet ink obtained by the method for producing an inkjet ink according to any one of claims 6 to 8.   The ratio of B to A is equal to or greater than A when the content of the self-dispersing pigment in the ink is A (mass%) and the content of the poor solvent in the ink is B (mass%). The ink for inkjet described in 2.   11. The inkjet recording method according to claim 1, wherein the ink is ejected from an orifice in accordance with a recording signal and recording is performed on a recording medium. An ink jet recording method, characterized by being an ink for use. An ink cartridge comprising an ink container containing ink, wherein the ink is the ink-jet ink according to any one of claims 1 to 5, 9, and 10. cartridge.

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