JP2008169272A - Water-based ink, inkjet recording method, ink cartridge, recording unit and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide water-based ink obtained by improving jetting stability and long-term preservation stability of resin dispersion type pigment ink, and providing satisfactory appearance quality of characters and bleeding resistance. <P>SOLUTION: The water-based ink containing a plurality of polymers and carbon black is regulated so that the plurality of the polymers may include a block copolymer and a random copolymer, and the ratio of the content A (mass%) of the block copolymer to the content B (mass%) of the random copolymer based on the whole mass of the ink may satisfy the relation of expression (1): 0.25≤A/B<1.5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aqueous ink, an ink jet recording method using such an aqueous ink, an ink cartridge, a recording unit, and an ink jet recording apparatus.

  As a water-based ink used in an ink jet recording apparatus, development of a pigment ink using a pigment as a coloring material has been vigorously advanced. Pigment inks can be broadly classified into inks containing self-dispersing pigments and inks containing resin-dispersed pigments. In recent years, due to the increasing demand for scratch resistance and marker resistance of recording parts, resin-dispersed pigment inks have been widely developed to provide the required performance by containing resin in the ink. .

  In the resin-dispersed pigment ink, viewpoints such as material selectivity, manufacturing stability, and cost are often emphasized as the resin for dispersing the pigment. For this reason, resins obtained by random copolymerization of vinyl monomers in a solvent, solvent-free, neutralized and dissolved, and dissolved in water (hereinafter referred to as random copolymers) are widely used (Patent Documents 1 to 3). 3). However, the resin-dispersed pigment ink using a random copolymer as a pigment dispersant has a problem that it may be inferior in ink ejection durability and long-term storage stability as compared with a dye ink. Therefore, various attempts have been made to improve the ejection stability and long-term storage stability of resin-dispersed pigment inks using random copolymers as dispersants.

Japanese National Patent Publication No. 10-502097 Japanese Patent No. 3053589 Japanese Patent No. 3188219

  The present inventors examined a graft copolymer using a carboxyl group-containing macromonomer described in Patent Document 1. However, this copolymer has a hydrophobic main chain portion and a hydrophilic side chain portion, and is excellent in stabilizing the dispersion of the pigment dispersion, but tends to increase the viscosity of the ink and is used as an ink for ink jet. To make it difficult.

  As a result of studying the pigment ink described in Patent Document 2, although the ink ejection stability and long-term storage stability can be improved, the character quality and bleeding resistance of the recorded matter have reached satisfactory levels. There wasn't. In other words, ink containing pigment dispersed with a block copolymer reduces the swelling phenomenon of the face surface (the surface with the ejection port for ejecting ink), which reduces the ink ejection stability, and stabilizes the ink for long-term storage. There is an effect on sex. However, it has been found that character quality and bleeding resistance tend to decrease.

  Patent Document 3 discloses a method for producing an aqueous pigment dispersion in which a random copolymer is present at 1 to 100 parts by mass per 100 parts by mass of a block copolymer. However, as a result of the study of the pigment dispersion and the pigment ink by the present inventors, a desired level of character quality and bleeding resistance could not be obtained.

  Accordingly, an object of the present invention is to improve the ejection stability and long-term storage stability of resin-dispersed pigment ink, which is a problem of the prior art, and a water-based ink (hereinafter simply referred to as “ink”) that can satisfy character quality and bleeding resistance. Is sometimes called). Another object of the present invention is to provide an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus using the ink.

  On the other hand, as a result of intensive studies on means for solving the above-mentioned problems, the present inventors have paid attention to an ink containing a block copolymer and a random copolymer at a specific ratio. As a result, the present inventors have found that an ink having good ink ejection stability and long-term storage stability, and good character quality and bleeding resistance can be obtained without causing the face surface slipping phenomenon. That is, the inventors have found an ink characterized in that the ratio of block copolymer to random copolymer is block copolymer / random copolymer = 0.25 or more and less than 1.5, and have completed the present invention.

The above object is achieved by the present invention described below. That is, the present invention is an ink containing a plurality of polymers and carbon black, wherein the plurality of polymers includes a block copolymer and a random copolymer, and the content A (mass of the block copolymer based on the total mass of the ink). %) And the content B (mass%) of the random copolymer satisfy the relationship of the following formula (1).

  The present invention also provides an ink jet recording method for recording on a recording medium by ejecting ink by an ink jet method, wherein the ink is the ink of the present invention.

  According to another aspect of the present invention, there is provided an ink cartridge including an ink storage portion that stores ink, wherein the ink is the ink of the present invention.

  According to another aspect of the present invention, there is provided a recording unit including an ink storage portion storing ink and a recording head for discharging ink, wherein the ink is the ink of the present invention. Provide units.

  According to the present invention, in an ink jet recording apparatus including an ink storage portion that stores ink and a recording head for discharging ink, the ink is the ink of the present invention. An ink jet recording apparatus is provided.

  According to the present invention, the ink surface is excellent in ink ejection stability and long-term storage stability without causing a nuisance phenomenon on the face surface (hereinafter sometimes referred to as “face surface nuisance”). Ink with excellent properties can be provided. Further, according to another embodiment of the present invention, an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus using such ink can be provided.

  Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention. The ink of the present invention contains a block copolymer, a random copolymer, and carbon black (hereinafter sometimes simply referred to as “pigment”). Furthermore, when the content of the block copolymer based on the total mass of the ink is A and the content of the random copolymer is B, 0.25 ≦ A / B <1.5. The reason why the two polymers are used in combination in the ink of the present invention is that the ink ejection stability, long-term storage stability, and good character quality and bleeding resistance of the color ink as described above are satisfied. Because. These will be described in more detail.

  First, the characteristics and differences between the random copolymer and the block copolymer will be described. In the random copolymer, each of the hydrophobic unit and the hydrophilic unit is composed of one monomer unit, and these units are irregularly arranged in the molecule. Since the hydrophilic unit of the polymer dissolved by neutralization is soluble in water, the polymer chain is expanded in water. On the other hand, since the hydrophobic unit is insoluble in water, the polymer chain is shrunk and forms minute micelles that cannot be visually determined. However, the hydrophobic unit is not stable because it is minute. That is, the random copolymer is a mixture of monomer units that are actually soluble in water and monomer units that are insoluble in water. However, the high degree of dissociation of solubilizing groups (for example, carboxyl groups) in water compensates for the presence of unstable minute micelles formed by hydrophobic units, and they are present in a clear liquid visually. It is possible.

  On the other hand, the block copolymer is different from the random copolymer described above, and the hydrophobic unit and the hydrophilic unit are each composed of several monomers, and these units are regularly arranged in the molecule. Usually, a block copolymer suitable for an ink applied to an ink jet recording method is a copolymer having the following constitution. That is, it is an AB block type in which hydrophobic units (referred to as A blocks) and ionic hydrophilic units (referred to as B blocks) are localized. Or it is the ABC block type which added the nonionic hydrophilic unit (it calls a C block) to the above-mentioned AB block type.

  Block copolymers have larger hydrophilic and hydrophobic units than those of random copolymers. For this reason, the block copolymer dissolved by neutralization is in a state where polymer units soluble in water and polymer units insoluble in water are localized, so to speak to behave like a high molecular weight surfactant. Conceivable. Therefore, the block copolymer has the characteristics that the polymer chain spread in water is small and the micelle formed by the hydrophobic unit is large compared to the random copolymer.

  In preparing the ink of the present invention, a pigment dispersion is first prepared. The polymer used in the pigment dispersion may be a random copolymer, a block copolymer, or a combination of a random copolymer and a block copolymer. However, in the present invention, it is preferable to use a random copolymer from the viewpoint of stably producing a pigment dispersion and long-term storage stability of the ink. The present inventors consider this reason as follows.

  There are three elements necessary for the dispersion of the pigment: 1) imparting wettability to the pigment by the polymer, 2) mechanical force (crushing the aggregated pigment), and 3) stabilizing the adsorption of the polymer to the pigment. . Here, since block copolymers tend to form stable micelles compared to random copolymers, polymer hydrophobic units suitable for adsorption to pigments that are insoluble (hydrophobic) in water, such as carbon black, are polymers. It is hard to appear on the surface. That is, the micelle formed by the block copolymer has a small specific surface area. Therefore, it is not suitable for imparting wettability to the pigment of 1), and particularly not suitable for stabilizing adsorption to the pigment of 3). Therefore, the ink of the present invention is preferably prepared using a pigment dispersion dispersed with a random copolymer.

  When the pigment is dispersed with a random copolymer, the ratio (mass ratio) between the pigment and the random copolymer is preferably pigment / random copolymer = 1.0 or more and less than 6.0. If this ratio is less than 1.0, the ratio of the resin is too high, the viscosity of the pigment dispersion becomes high, and the dispersibility of the pigment may deteriorate. On the other hand, if the ratio is 6.0 or more, the ratio of the resin is too small and a sufficient amount of the resin to be adsorbed on the pigment surface cannot be secured, which may cause poor dispersion.

  The ink of the present invention is characterized by using a block copolymer and a random copolymer in combination. Then, as described above, an ink can be prepared by adding a pigment dispersion using a random copolymer as a dispersant and a block copolymer to an aqueous medium (additives may be further used as necessary). preferable. In the present invention, the ratio of the content A (% by mass) of the block copolymer to the content B (% by mass) of the random copolymer based on the total mass of the ink is expressed as block copolymer / random copolymer (A / B) = It must be 0.25 or more and less than 1.5. Hereinafter, those reasons will be described in detail. First, the biggest reason for adding a block copolymer to an aqueous medium containing a pigment dispersion using a random copolymer is that sufficient ink ejection stability can be obtained using only the pigment dispersion using a random copolymer. Because there is no.

  In our study, when a pigment ink containing a pigment dispersion using a random copolymer is ejected from a recording head, especially when ejecting ink continuously for a long time, the pigment ink adheres to the face surface. I found it easy to do. The reason is that the pigment ink is in a state where the water is evaporated and concentrated when the ink is ejected, so that the dispersion stability is inferior to that in the ink cartridge. The minute micelles of the random copolymer formed by hydrophobic units cause hydrophobic interaction with the weakly water-repellent part on the face surface, so that the micelles are easy to adhere to the face surface, and the face surface slippage is reduced. I presumed that it was easier to cause.

  Next, a pigment ink prepared by adding an appropriate amount of a block copolymer to an aqueous medium containing a pigment dispersion using a random copolymer was ejected from a recording head. As a result, it was found that even when ink was ejected continuously for a long time, the amount of pigment ink adhering to the face surface was extremely reduced. The reason is that, as described above, since the block copolymer has a relatively large micelle as compared with the random copolymer, it tends to adhere to a portion where the water repellent treatment on the face surface is insufficient. Further, the micelle of the block copolymer has a smaller specific surface area than the micelle of the random copolymer, and the adhesion force to the face surface is also small. Therefore, even if the block copolymer adheres with a weak adhesion force, it can be presumed that the face surface is less likely to squeeze because it has a characteristic of being removed relatively easily.

  Furthermore, because block copolymers have the ability to behave like high molecular weight surfactants, the effect of peeling pigment ink containing a pigment dispersion using a random copolymer once attached to the face surface from the face surface, so to speak. It is conceivable that an effect appears. For this reason, from the viewpoint of improving the ejection stability of ink, the larger the amount of the added block copolymer, the better. Specifically, the ratio of the block copolymer content A (% by mass) to the random copolymer content B (% by mass) based on the total mass of the ink is such that the block copolymer / random copolymer (A / B) = 0. It is preferably 25 or more, more preferably 0.30 or more.

  The smaller the content of the block copolymer in the ink, the better the character quality and bleeding resistance of the recording with the ink of the present invention. The reason is that the random copolymer has a low micelle forming ability, so that the color materials are quickly aggregated in the process in which the aqueous medium in the ink applied on the recording medium evaporates and the color material is fixed. On the other hand, it is considered that the block copolymer has a high micelle forming ability, and thus aggregation of the coloring materials is slow. Therefore, the ratio of the block copolymer content A (% by mass) and the random copolymer content B (% by mass) based on the total mass of the ink is less than block copolymer / random copolymer (A / B) = 1.5. Furthermore, it is preferable that it is less than 1.35.

  In summary, in the present invention, the ratio of the block copolymer content A (% by mass) and the random copolymer content B (% by mass) based on the total mass of the ink preferably satisfies the following requirements. . That is, the block copolymer / random copolymer (A / B) is preferably 0.25 or more and less than 1.5, and more preferably 0.30 or more and less than 1.35. If the ratio (A / B) is less than 0.25, it is not preferable because the face surface may be dulled and the ink ejection stability may deteriorate. Further, if the ratio (A / B) is 1.5 or more, the character quality and bleeding resistance may deteriorate, which is not preferable.

  Further, when the carbon black content based on the total mass of the ink is C (mass%), the C (mass%), the content A (mass%) of the block copolymer and the random copolymer contained The amount B (% by mass) preferably satisfies the following requirements. That is, in the present invention, the content of carbon black / [total content of block copolymer and random copolymer] (C / (A + B)) = 0.67 or more and less than 2.0 is preferable. When the ratio (C / (A + B)) is less than 0.67, the resin content is higher than the pigment content, and the resin that is not adsorbed by the pigment increases. For this reason, even if the ratio of block copolymer / random copolymer (A / B) is 0.25 or more and less than 1.5 as described above, the face surface is liable to swell, and the ink ejection stability may be inferior. This is not preferable. If the ratio (C / (A + B)) is 2.0 or more, the resin content is less than the pigment content, so the long-term storage stability and ejection stability of the ink may deteriorate. This is not preferable.

  The acid value of the random copolymer used in the present invention is preferably in the range of 100 mgKOH / g or more and less than 160 mgKOH / g. If the acid value is less than 100 mgKOH / g, the solubility in water is poor and the ink may become cloudy, which is not preferable. Further, if the acid value is 160 mgKOH / g or more, the solubility in water is too high, and the ink penetrates quickly into the recording medium, which may be inferior in character quality and bleeding resistance.

  The acid value of the block copolymer used in the present invention is preferably in the range of 130 mgKOH / g or more and less than 230 mgKOH / g. If the acid value is less than 130 mgKOH / g, it is not preferable because the face surface is liable to be dull and ink ejection stability may be inferior. The reason is considered to be that although the solubility of the resin in water is sufficient, the effect due to the behavior like a high molecular weight surfactant cannot be obtained. Further, when the acid value is 230 mgKOH / g or more, the solubility in water is too high and the ink penetrates quickly into the recording medium as in the case of the random copolymer, so that the character quality and bleeding resistance are inferior. Since there are cases, it is not preferable.

  The random copolymer used in the present invention preferably has a weight average molecular weight in the range of 4,000 to less than 25,000. If the weight average molecular weight is less than 4,000, pigment dispersion is likely to occur, which is not preferable. The reason for this is considered to be that when the pigment is dispersed, the three-dimensional repulsion layer of the resin is thin, and the adsorption stabilization of the polymer to the pigment is insufficient. Further, even if the weight average molecular weight is 25,000 or more, poor dispersion may occur easily, which is not preferable. The reason is thought to be that it is difficult to obtain a sufficient shearing force when dispersing the pigment.

  The block copolymer used in the present invention preferably has a weight average molecular weight in the range of 2,000 or more and less than 15,000. If the weight average molecular weight is less than 2,000, the ink ejection stability may be inferior, which is not preferable. The reason for this is thought to be that when the molecular weight is low, the effect due to the behavior like a high molecular weight surfactant cannot be obtained sufficiently, and it is particularly difficult to remove the random copolymer that easily adheres to the face surface. . Moreover, since the said weight average molecular weight is 15,000 or more, since it may be inferior to long-term storage stability, it is unpreferable. The reason is that although the surface-active effect is sufficient, it is easy to interact with the random copolymer, and the physical properties are likely to change when stored for a long time.

  As long as the ink of the present invention satisfies each of the above-mentioned characteristics, the characteristics of the raw materials used and the production method are not particularly specified, but examples of preferred forms will be specifically described.

(Carbon black dispersion)
The carbon black dispersion liquid (hereinafter sometimes simply referred to as “pigment dispersion liquid”) will be described. The ink of the present invention is characterized by containing two kinds of polymers (random copolymer and block copolymer). As long as the pigment dispersion contained in the ink satisfies the above-described characteristics, the characteristics of the material used and the manufacturing method are not particularly specified. As described above, the polymer used in the pigment dispersion may be a random copolymer, a block copolymer, or a combination of a random copolymer and a block copolymer. However, in the present invention, it is particularly preferable to use a random copolymer as the polymer used in the pigment dispersion from the viewpoint of stably producing the pigment dispersion and long-term storage stability of the ink. Furthermore, the block copolymer or random copolymer is preferably an acrylic polymer, and in particular, both the block copolymer and the random copolymer are preferably acrylic polymers.

  Examples of the random copolymer or block copolymer include copolymers composed of at least two monomers (of which at least one is a hydrophilic monomer) among the hydrophobic monomers and hydrophilic monomers listed below, or salts thereof.

  Specific examples of the hydrophobic monomer include the following (meth) acrylic acid esters. Examples include methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-propyl, acrylic acid-n-butyl, acrylic acid-t-butyl, and benzyl acrylate. Moreover, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylate-n-propyl, methacrylate-n-butyl, isobutyl methacrylate, tert-butyl methacrylate, tridecyl methacrylate, benzyl methacrylate, and the like.

  Further, styrene monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and p-tert-butylstyrene are exemplified. Further, itaconic acid esters such as benzyl itaconic acid; maleic acid esters such as dimethyl maleate; fumaric acid esters such as dimethyl fumarate; acrylonitrile, methacrylonitrile, vinyl acetate and the like.

  As the hydrophilic monomer, it is preferable to use a monomer having an anionic group and a monomer having a nonionic group. Specifically, examples of the monomer having an anionic group include the following. Examples thereof include monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid and fumaric acid, or salts thereof.

  In addition, a monomer having a sulfonic acid group such as styrene sulfonic acid, sulfonic acid-2-propylacrylamide, acrylic acid-2-ethyl sulfonate, ethyl methacrylic acid-2-sulfonic acid, butylacrylamide sulfonic acid, or a salt thereof. Can be mentioned. Moreover, the monomer etc. which have phosphonic acid groups, such as methacrylic acid-2-ethyl phosphonate and acrylic acid-2-ethyl phosphonate, are mentioned. Among these, it is preferable to use acrylic acid or methacrylic acid, particularly acrylic acid, that is, use an acrylic polymer.

  Specific examples of the monomer having a nonionic group include the following. Examples include monomers having a radically polymerizable unsaturated bond and a hydroxyl group exhibiting strong hydrophilicity in the structure such as hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, and hydroxylpropyl (meth) acrylate. It is done.

  In addition, monomers containing an alkylene oxide group can be used. Specific examples include the following. Examples thereof include methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, and polypropylene glycol (meth) acrylate.

  In addition, various known or novel oligomers, macromonomers and the like can be used without limitation. Among these, styrene or a copolymer of benzyl methacrylate and acrylic acid or methacrylic acid is preferable because it is inexpensive and can be polymerized relatively easily.

  Production of the random copolymer and block copolymer used in the ink of the present invention can be carried out by a general method. For example, the block copolymer can be produced by a cation living polymerization method, a group transfer polymerization method, an atom transfer polymerization method, a method using a polymer azo polymerization initiator, or the like. Of course, in the present invention, any polymer obtained by any method can be used as long as it satisfies the above requirements.

  In addition, both the liquid containing the random copolymer and the liquid containing the block copolymer are subjected to solvent removal under conditions such as reduced pressure to remove the unreacted monomer and the solvent used in the polymerization. Thereafter, it is preferably neutralized with a base such as sodium hydroxide, potassium hydroxide, ammonia or dimethylethanolamine and used as a state dissolved in water (alkali-soluble resin).

  The method for producing the pigment dispersion (dispersing the pigment) is not limited by any method as long as it is a commonly used dispersion method, and examples thereof include the following. Examples thereof include a method using a disperser such as a paint shaker, a sand mill, a bead mill, an agitator mill, and a three roll mill, a high-pressure homogenizer such as a microfluidizer, nanomizer, and optimizer, and an ultrasonic disperser. Among these, it is particularly preferable to use a bead mill from the viewpoints of simplicity and dispersion stability. The bead mill conditions are not particularly limited, but the following conditions are preferable.

・ Bead filling ratio: 50% to 90%
・ Bead diameter: 0.1mm to 1mm
・ Rotation speed: 300rpm to 5,000rpm
・ Dispersion time: 0.1 to 24 hours

  Like the ink of the present invention, the ink contains a plurality of polymers and their contents can be confirmed by a conventional method using gel permeation chromatography (GPC) or the like. At this time, if the difference in the weight average molecular weight of the plurality of polymers is about 1,000, quantification can be performed with higher accuracy.

(Carbon black)
The carbon black that can be used in the ink of the present invention is not particularly limited, and any of the following can be used. In the present invention, the content (mass%) of carbon black in the ink is 0.1 mass% or more and 15.0 mass% or less, more preferably 1.0 mass% or more and 10.0 mass%, based on the total mass of the ink. It is preferable that it is below mass%.

  As carbon black, carbon black, such as furnace black, lamp black, acetylene black, channel black, can be used, for example. Specifically, the following can be used.

  Ray Van: 1170, 1190, ULTRA-II, 1200, 1255, 1250, 1500, 2000, 3500, 5000, ULTRA, 5250, 5750, 7000, etc. (made in Colombia). Black Pearls L, Legal: 330R, 400R, 660R, Mogul L, Monak: 700, 800, 880, 900, 1000, 1100, 1300, 1400, 2000, Vulcan XC-72R, etc. (manufactured by Cabot).

  Color Black: FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex: 35, U, V, 140U, 140V, Special Black: 4, 4A, 5, 6 etc. (manufactured by Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA7, MA8, MA100, MA600, etc. (manufactured by Mitsubishi Chemical). In addition, carbon black newly prepared for the present invention, magnetic fine particles such as magnetite and ferrite, titanium black, and the like can also be used.

(Aqueous medium)
In the ink of the present invention, water or an aqueous medium containing water and a water-soluble organic solvent can be used. The content (% by mass) of the water-soluble organic solvent in the ink is 3.0% by mass or more and 60.0% by mass or less, and further 5.0% by mass or more and 45.0% by mass or less based on the total mass of the ink. It is preferable that Specifically, the following water-soluble organic solvents can be used.

  Alkanols having 1 to 4 carbon atoms such as ethanol, isopropanol, n-butanol, isobutanol, secondary butanol and tertiary butanol. Carboxylic acid amides such as N, N-dimethylformamide and N, N-dimethylacetamide. Ketones or ketoalcohols such as acetone, methyl ethyl ketone, 2-methyl-2-hydroxypentan-4-one; Cyclic ethers such as tetrahydrofuran and dioxane. Glycols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- or 1,3-propylene glycol, 1,2- or 1,4-butylene glycol, thiodiglycol. 1,5-pentanediol, 1,2- or 1,6-hexanediol, 1,2,6-hexanetriol, polyethylene glycol having an average molecular weight of 200, 400, 600, 1,000, 2,000, etc. Polyhydric alcohols. Heterocycles such as 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylmorpholine. Sulfur-containing compounds such as dimethyl sulfoxide. Sugars such as glucose and galactose. These water-soluble organic solvents may be used alone or in combination of two or more.

  Moreover, it is preferable to use deionized water. The content (% by mass) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink.

(Other additives)
The ink of the present invention may contain a solid moisturizing compound such as urea, ethylene urea, trimethylol propane, trimethylol ethane, etc., if necessary, in addition to the components described above. Moreover, you may contain various additives, such as surfactant, a pH adjuster, a rust preventive agent, antiseptic | preservative, an antifungal agent, antioxidant, a reduction inhibitor, an evaporation accelerator, and a chelating agent.

(Ink characteristics)
The ink of the present invention having the configuration as described above preferably has a characteristic that it can be favorably ejected from the recording head. For this reason, the ink has, for example, a viscosity of 1 mPa · s or more and 8 mPa · s or less, a surface tension of 30 mN / m or more and 50 mN / m or less, and a liquid contact property with each member constituting the ink jet recording apparatus. From the viewpoint, the pH is preferably 6.0 or more and 9.5 or less. In order to obtain desired characteristics, the pigment dispersion and the ink in the ink of the present invention are preferably purified by a method such as centrifugation or filtration with a filter. As long as the method is generally used, any method can be used without limitation. Among them, the purification of the pigment dispersion is preferably performed by removing coarse particles with a centrifugal separator, and the purification of the ink is preferably performed by pressure filtration with a filter.

<Color ink>
The ink of the present invention can also be used as an ink set with other inks, for example, color inks. The color ink will be described below. The color ink preferably contains at least water, a water-soluble organic solvent, and a coloring material. As the color ink, any conventionally known ink-jet ink can be used.

(Coloring material)
As the color material of the color ink, a dye or a pigment can be used. The color of the color ink can be appropriately selected from, for example, cyan, magenta, yellow, red, green, blue, orange, and the like.

[Organic pigments]
The pigment used for the color ink is preferably an organic pigment. Specifically, the following can be used as the organic pigment.
Water-insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, and Pyrazolone Red. Water-soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon. Phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green.

  Quinacridone pigments such as quinacridone red and quinacridone magenta. Perylene pigments such as perylene red and perylene scarlet. Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange. Imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange, and benzimidazolone red. Pilanthrone pigments such as pyranthrone red and pyranthrone orange. Indigo pigment. Condensed azo pigment. Thioindigo pigment. Flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, etc.

Further, when the organic pigment is represented by a color index (CI) number, specifically, the following can be used.
C. I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 151, 153, 154, 166 168 etc. C. I. Pigment Orange: 16, 36, 43, 51, 55, 59, 61, 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, etc. C. I. Pigment violet: 19, 23, 29, 30, 37, 40, 50, and the like. C. I. Pigment Blue: 15, 15: 3, 15: 1, 15: 4, 15: 6, 22, 60, 64, and the like. C. I. Pigment Green: 7, 36, etc. C. I. Pigment Brown: 23, 25, 26, etc.

〔dye〕
Examples of the dye that can be used in the ink of the present invention include a direct dye, an acid dye, a reactive dye, and a basic dye. Moreover, even if it is a dye which is not described in a color index, if it has water solubility, it can be used. When the dye is indicated by a color index (CI) number, specifically, the following can be used.

[Yellow dye]
C. I. Direct yellow: 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110, 132, etc. C. I. Acid Yellow: 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99, etc. C. I. Reactive yellow: 2, 3, 4, 17, 25, 37, etc. C. I. Food yellow: 3 etc.

[Magenta dye]
C. I. Direct Red: 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226 227, 228, 229, 230, etc. C. I. Acid Red: 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 106, 114, 115, 133, 134, 145 158, 198, 249, 265, 289, etc. C. I. Food Red: 87, 92, 94, etc. C. I. Direct violet 107 and the like.

[Cyan dye]
C. I. Direct blue: 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226, 307, etc. C. I. Acid Blue: 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 112, 117, 127, 138, 158 161, 203, 204, 221, 244, etc.

[Black dye]
C. I. Direct black: 17, 19, 22, 31, 32, 51, 62, 71, 74, 112, 113, 154, 168, 195, etc. C. I. Acid Black: 2, 48, 51, 52, 110, 115, 156, etc. C. I. Food black: 1, 2, etc.

(Characteristics of aqueous media and additives, color ink)
As the aqueous medium and additive for the color ink, the same aqueous medium and additive used in the ink of the present invention described above can be used. Further, it is preferable that the color ink has a characteristic that it can be discharged well from the recording head. For this reason, the ink has a viscosity of 1 mPa · s or more and 8 mPa · s or less, a surface tension of 25 mN / m or more and 45 mN / m or less, and from the viewpoint of liquid contact with each member constituting the ink jet recording apparatus. The pH is preferably from 6.0 to 9.5.

<Inkjet recording method, ink cartridge, recording unit, and inkjet recording apparatus>
Next, an example of an ink jet recording apparatus will be described below. First, FIG. 1 and FIG. 2 show an example of the configuration of a recording head that is a main part of an ink jet recording apparatus using thermal energy. FIG. 1 is a cross-sectional view of the recording head 13 along the ink flow path, and FIG. 2 is a cross-sectional view taken along the line AB of FIG. The recording head 13 is obtained by adhering a heating element substrate 15 and a glass, ceramic, silicon or plastic plate having a flow path (nozzle) 14 through which ink passes.

The heating element substrate 15 includes a protective layer 16, electrodes 17-1 and 17-2, a heating resistor layer 18, a heat storage layer 19, and a substrate 20. The protective layer 16 is made of silicon oxide, silicon nitride, silicon carbide, or the like. The electrodes 17-1 and 17-2 are made of aluminum, gold, aluminum-copper alloy, or the like. The heating resistor layer 18 is formed of a high melting point material such as HfB ₂ , TaN, TaAl or the like. The heat storage layer 19 is formed of thermal silicon oxide, aluminum oxide, or the like. The substrate 20 is made of a material with good heat dissipation such as silicon, aluminum, or aluminum nitride.

  When a pulsed electrical signal is applied to the electrodes 17-1 and 17-2 of the recording head 13, the region indicated by n of the heating element substrate 15 rapidly generates heat, and the ink 21 in contact with the surface is in contact with the ink 21. Bubbles are generated. Then, the meniscus 23 protrudes due to the pressure of the bubbles, and the ink 21 is ejected through the nozzle 14 of the recording head, becomes an ink droplet 24 from the ejection orifice 22, and flies toward the recording medium 25.

  FIG. 3 is an external view of an example of a multi-head in which a large number of recording heads shown in FIG. 1 are arranged. This multi-head is made by adhering a glass plate 27 having multi-nozzles 26 and a heating head 28 similar to that described in FIG.

  FIG. 4 is an example of an ink jet recording apparatus incorporating this recording head. In FIG. 4, one end of a blade 61, which is a wiping member, is held and fixed by a blade holding member, and forms a cantilever. The blade 61 is disposed at a position adjacent to the recording area by the recording head 65, and in the illustrated example, is held in a form protruding in the moving path of the recording head 65. Reference numeral 62 denotes a cap on the discharge port surface of the recording head 65, which is disposed at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, contacts the ink discharge port surface, and capping. The structure to perform is provided.

  Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61 and, like the blade 61, is held in a form protruding in the moving path of the recording head 65. The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery unit 64, and the blade 61 and the ink absorber 63 remove moisture, dust, and the like from the ejection port surface. Reference numeral 65 denotes a recording head which has discharge energy generating means and performs recording by discharging ink onto a recording medium facing the discharge port surface where the discharge port is arranged. Reference numeral 66 denotes a movement of the recording head 65 by mounting the recording head 65. It is a carriage for performing.

  The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording area and its adjacent area can be moved by the recording head 65. 51 is a paper feed section for inserting a recording medium, and 52 is a paper feed roller driven by a motor (not shown). With these configurations, the recording medium is fed to a position facing the discharge port surface of the recording head 65, and discharged to a paper discharge unit provided with a paper discharge roller 53 as recording progresses.

  In the above configuration, when recording is completed and the recording head 65 returns to the home position, the cap 62 of the ejection recovery unit 64 is retracted from the movement path of the recording head 65, but the blade 61 protrudes into the movement path. Yes. As a result, the ejection port of the recording head 65 is wiped. When the cap 62 is in contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the moving path of the recording head. When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are present at the same position as the above-described wiping position.

  As a result, the ejection port surface of the recording head 65 is wiped even during this movement. The above-described movement of the recording head 65 to the home position is not only at the end of recording or at the time of recovery of ejection, but also at the home position adjacent to the recording area at a predetermined interval while the recording head moves through the recording area for recording. The wiping is performed along with this movement.

  FIG. 5 is a diagram illustrating an example of an ink cartridge that contains ink supplied to the recording head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink container, for example, an ink bag, in which supply ink is stored, and a rubber plug 42 is provided at the tip thereof. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the recording head. An ink absorber 44 receives waste ink.

  The ink jet recording apparatus is not limited to the one in which the recording head and the ink cartridge are separated as described above, but is also suitable for an apparatus in which the recording head and the ink cartridge are integrated as shown in FIG. Used. In FIG. 6, the recording unit 70 stores an ink storage portion for storing ink, for example, an ink absorber, and the ink in the ink absorber is transferred from the recording head portion 71 having a plurality of ejection openings. It is configured to be ejected as droplets.

  Further, the ink storage portion may be an ink bag having a spring or the like inside without using an ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere. The recording unit 70 is used in place of the recording head 65 shown in FIG. 4 and is detachable from the carriage 66.

  Next, a preferable example of an ink jet recording apparatus using mechanical energy includes one having an on-demand type ink jet recording head having the following configuration. Specifically, the ink jet recording apparatus includes a nozzle forming substrate having a plurality of nozzles, and a pressure generating element formed of a piezoelectric material and a conductive material disposed to face the nozzles. Then, ink filling the periphery of the pressure generating element is provided, the pressure generating element is displaced by the applied voltage, and ink droplets are ejected from the nozzles. An example of the configuration of a recording head which is a main part of the above-described ink jet recording apparatus is shown in FIG.

  The recording head includes an ink flow path 80, an orifice plate 81, a vibration plate 82, a piezoelectric element 83, an orifice plate 81, a vibration plate 82, and a substrate 84 for fixing the support. Ink is ejected as ink droplets having a desired volume through an orifice plate 81 from an ink flow path 80 communicating with an ink chamber (not shown). At this time, the ink is ejected by the action of a vibration plate 82 that applies pressure, and a piezoelectric element 83 that is bonded to the vibration plate 82 and is displaced by an electric signal. The ink flow path 80 is formed of a photosensitive resin or the like.

  In the orifice plate 81, a discharge port 85 is formed by drilling a metal such as stainless steel or nickel by electroforming or pressing. The diaphragm 82 is formed of a metal film such as stainless steel, nickel, or titanium and a highly elastic resin film.

  The piezoelectric element 83 is made of a dielectric material such as barium titanate or PZT. The recording head having the above-described configuration generates strain stress by applying a pulse voltage to the piezoelectric element 83. The energy deforms the vibration plate bonded to the piezoelectric element 83, pressurizes the ink in the ink flow path 80 vertically, and discharges ink droplets (not shown) from the discharge port 85 of the orifice plate 81 for recording. Works to do. Such a recording head can be used by being incorporated in an ink jet recording apparatus similar to that shown in FIG. The detailed operation of the ink jet recording apparatus can be the same as described above.

  Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited by the following Example, unless the summary is exceeded. In the text, “parts” and “%” are based on mass unless otherwise specified.

[Production Example 1 (Preparation of random copolymer)]
200 parts of ethylene glycol monobutyl ether was added to a four-necked flask equipped with a stirrer, a reflux cooling device, and a nitrogen gas introduction tube, nitrogen gas was introduced, and the temperature was raised to 130 ° C. while stirring. Thereafter, a mixture containing 65 parts of styrene, 25 parts of acrylic acid, 10 parts of n-butyl acrylate and 4 parts of t-butyl peroxide as a polymerization initiator was added dropwise over 3 hours. After completion of the dropping, aging was performed for 2 hours, and ethylene glycol monobutyl ether was removed under reduced pressure. The obtained solid polymer was dissolved by adding potassium hydroxide and ion exchange water equivalent to its acid value and neutralizing at 80 ° C. to dissolve, so that the resin solid content was 15%, the acid value was 190 mgKOH / g, and the weight average A random copolymer A having a molecular weight of 6,000 was obtained.

[Production Examples 2 and 3 (Preparation of random copolymer)]
By changing to the composition shown in Table 1 in the same manner as in Production Example 1, random copolymers B and C having a resin solid content of 15% were obtained.

[Production Example 4 (Preparation of block copolymer)]
70 parts of ethylene glycol monobutyl ether was added to a four-necked flask equipped with a stirrer, a reflux cooling device and a nitrogen gas introduction tube, nitrogen gas was introduced, and the temperature was raised to 165 ° C. while stirring. Thereafter, 20 parts of methacrylic acid-n-butyl, 80 parts of methacrylic acid, 20 parts of 2,4-diphenyl-4-methyl-1-pentene (α-methylstyrene dimer), 30 parts of ethylene glycol monobutyl ether and azo as a polymerization initiator A mixture containing 4 parts of bisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 3 hours. A macromonomer having a resin solid content of 50% and a weight average molecular weight of 2,500 was prepared by aging for 2 hours after the completion of the dropping.

  Next, the temperature of the reaction vessel was set to 130 ° C., and a mixture containing 180 parts of benzyl methacrylate, 20 parts of n-butyl methacrylate and 6 parts of t-butyl peroxide as a polymerization initiator was added dropwise over 3 hours. . After completion of the dropping, aging was performed for 2 hours, and ethylene glycol monobutyl ether was removed under reduced pressure. The obtained solid polymer was dissolved by adding potassium hydroxide and ion-exchanged water equivalent to its acid value and neutralizing at 80 ° C. to obtain a resin solid content of 15%, acid value of 167 mgKOH / g, weight average A block copolymer D having a molecular weight of 8,000 was obtained.

[Production Examples 5 and 6 (Preparation of block copolymer)]
Block copolymers E and F having a resin solid content of 15% were obtained by changing the monomers used after preparing the macromonomer to the composition shown in Table 2 in the same manner as in Production Example 4.

[Preparation of pigment dispersion]
20 parts of carbon black, 10 parts of random copolymer A and 70 parts of water were dispersed at 1,500 rpm for 3 hours in a bead mill (LMZ2; manufactured by Ashizawa Finetech). 0.1 mm diameter zirconia beads were used, and the filling rate in the pot was 85%. As the carbon black, Black Pearls 880 (manufactured by Cabot) was used. Thereafter, the mixture was centrifuged at 5,000 rpm for 30 minutes to remove agglomerated components, and diluted with ion-exchanged water to obtain pigment dispersion 1 having a pigment concentration of 15%.

  Pigment dispersions 2 to 4 having a pigment concentration of 15% were obtained by changing the composition shown in Table 3 by the same method as described above.

[Preparation of ink]
The following components were mixed, and further filtered under pressure with a membrane filter (HDCII filter; manufactured by Pall) having a pore size of 2.5 microns to prepare ink 1 of the present invention.
・ Pigment dispersion 1 (including 1.5 parts of random copolymer A) 20 parts ・ Block copolymer D 1 part ・ Glycerin 5 parts ・ Polyethylene glycol (average molecular weight 600) 5 parts ・ Trimethylolpropane 5 parts ・ Acetylenol EH (trade name: (Made by Kawaken Fine Chemicals) 0.25 parts, ion-exchanged water balance The inks 2 to 9 of the present invention and the inks 1 and 2 of the comparative examples were similarly blended with the pigment dispersions and polymers shown in Tables 4 and 5 below. Got.

[Preparation of cyan pigment ink]
Cyan pigment inks used in Examples and Comparative Examples were prepared as follows. First, a mixed solution containing 20 parts of cyan pigment, 10 parts of random copolymer A and 70 parts of water was dispersed with a bead mill (LMZ2; manufactured by Ashizawa Finetech) at 1,800 rpm for 5 hours. In the bead mill, zirconia beads having a diameter of 0.1 mm were used, and the filling rate in the pot was 85%. The pigment used was a cyan pigment (Inkjet Cyan BG; manufactured by Clariant). Thereafter, the mixture was centrifuged at 5,000 rpm for 30 minutes to remove agglomerated components, and diluted with ion-exchanged water to obtain a cyan pigment dispersion having a pigment concentration of 15%. The cyan pigment dispersion obtained above was mixed with the following composition so that the colorant concentration in the ink was 3%, and further pressed with a membrane filter (HDCII filter; manufactured by Pall) having a pore size of 2.5 microns. Filtration was performed to prepare a cyan pigment ink.

・ Glycerol 7 parts ・ Polyethylene glycol (average molecular weight 1,000) 2 parts ・ Trimethylolpropane 3 parts ・ Ethylene glycol 5 parts ・ Acetylenol EH (trade name: manufactured by Kawaken Fine Chemicals) 0.7 part ・ Ion-exchanged water remaining

[Preparation of magenta pigment ink]
A magenta pigment ink was obtained by changing the pigment to a magenta pigment (Inkjet Magenta EO 02; manufactured by Clariant) and the colorant concentration in the ink to 4% in the same manner as in the preparation of the cyan pigment ink.

[Preparation of yellow pigment ink]
In the same manner as in the preparation of the cyan pigment ink, a yellow pigment ink was obtained by changing the pigment to yellow pigment (Hansa Brilliant Yellow 5GX; manufactured by Clariant) and the color material concentration in the ink to 4%.

[Ink characteristics]
<Long-term storage stability>
100 g of each ink was put into a 180 cc container made of Teflon (registered trademark), and the physical property values (d ₅₀ , d ₉₀ , viscosity) before and after being left to stand in a 60 ° C. oven in a sealed state for 3 months were measured. Judged by rate. In addition, the measuring method of a particle size is as follows. A liquid obtained by diluting each ink 1,000 times with pure water was prepared, and measured with a dynamic light scattering particle size distribution analyzer UPA-150EX (manufactured by Nikkiso) under the following conditions. The volume average particle diameter (d _The average particle size was evaluated at ₅₀ and d ₉₀ ) (average value of n3).
・ Setzero: 60s
・ Measurement time: 120s
-Number of measurements: 3 times-Refractive index of pigment: 1.8
The viscosity of each ink was measured with an E-type viscometer (RE80L; manufactured by Toyo Seiki Co., Ltd.) at 25 ° C. and a rotation speed of 50 rpm.

(Evaluation criteria)
AA: d ₅₀ , d ₉₀ , viscosity change rate is less than 10%.
A: Change rate of both d ₅₀ and d ₉₀ and viscosity is less than 15%.
B: Any one of d ₅₀ , d ₉₀ , and viscosity has a rate of change of 15% or more.
C: Change rate of 15% or more for all items.

[Ink evaluation method and evaluation results]
Tables 6 and 7 show the results obtained by mounting each of the inks obtained above on an ink jet recording apparatus, recording on a recording medium, and evaluating the ejection stability and bleeding resistance of the obtained image. A product name “PIXUS850i” (manufactured by Canon) was used for the ink jet recording apparatus, and a PPC paper (product name: office planner; manufactured by Canon) was used for the recording medium.

<Discharge stability>
Ejection stability was recorded by continuously printing 1,000 sheets of 2cm x 2cm solid images and images containing characters, by visual comparison of the initial recorded material and the last recorded material, and observation of the face surface after recording with an optical microscope. It was judged.
AA: 1,000 sheets can be recorded, and there is a slight difference in the dirt on the face surface between the initial stage and the end, but there is no deviation in the recorded matter.
A: 1,000 sheets can be recorded, and there is a slight difference in dirt on the face surface between the initial stage and the end, and there is a slight deviation in the recorded matter, but there is no problem in recording.
B: 1,000 sheets can be recorded, but the skew of the recorded matter and the stain on the face surface are conspicuous compared to the initial case.
C: 1,000 sheets cannot be recorded.

<Bleeding resistance>
Solid images of black and each color (yellow, magenta, cyan) were recorded adjacent to each other, the degree of bleeding between the black image and the color image was visually observed, and bleeding resistance was evaluated according to the following criteria. As the color ink, cyan pigment ink, magenta pigment ink, and yellow pigment ink obtained by the above-described methods were used.
AA: No bleeding.
A: Bleeding is hardly noticeable (color boundary is not blurred).
B: The bleeding is slightly conspicuous and the color boundary is blurred.
C: Bleeding is quite conspicuous and the color boundary is not known.

FIG. 2 is a longitudinal sectional view of a recording head. It is a cutaway view of the recording head. FIG. 2 is an external perspective view of a recording head in which the recording head shown in FIG. It is a perspective view which shows an example of an inkjet recording device. It is a longitudinal cross-sectional view of an ink cartridge. It is a perspective view which shows an example of a recording unit. FIG. 3 is a diagram illustrating an example of a configuration of a recording head.

Explanation of symbols

13: recording head 14: nozzle 15: heating element substrate 16: protective layer 17-1, 17-2: electrode 18: heating resistor layer 19: heat storage layer 20: substrate 21: ink 22: discharge orifice (micropore)
23: Meniscus 24: Ink droplet 25: Recording medium 26: Multi-nozzle 27: Glass plate 28: Heat generating head 40: Ink bag 42: Plug 44: Ink absorber 45: Ink cartridge 51: Paper feed unit 52: Paper feed roller 53 : Discharge roller 61: blade 62: cap 63: ink absorber 64: ejection recovery unit 65: recording head 66: carriage 67: guide shaft 68: motor 69: belt 70: recording unit 71: recording head unit 72: atmosphere communication Port 80: Ink channel 81: Orifice plate 82: Vibration plate 83: Piezoelectric element 84: Substrate 85: Ejection port

Claims (10)

A water-based ink containing a plurality of polymers and carbon black,
The plurality of polymers comprises block copolymers and random copolymers;
The ratio of the block copolymer content A (mass%) and the random copolymer content B (mass%) based on the total mass of the ink satisfies the relationship of the following formula (1). .

2. The water-based ink according to claim 1, wherein the carbon black content C (% by mass), the A, and the B based on the total mass of the ink satisfy the relationship of the following formula (2).

  The water-based ink according to claim 1 or 2, wherein the block copolymer is an acrylic polymer having an acid value of 130 mgKOH / g or more and less than 230 mgKOH / g.   The water-based ink according to any one of claims 1 to 3, wherein the block copolymer is an acrylic polymer having a weight average molecular weight of 2,000 or more and less than 15,000.   The water-based ink according to any one of claims 1 to 4, wherein the random copolymer is an acrylic polymer having an acid value of 100 mgKOH / g or more and less than 160 mgKOH / g.   The water-based ink according to any one of claims 1 to 5, wherein the random copolymer is an acrylic polymer having a weight average molecular weight of 4,000 or more and less than 25,000.   7. An ink jet recording method for recording on a recording medium by ejecting ink by an ink jet method, wherein the ink is the water-based ink according to any one of claims 1 to 6.   7. An ink cartridge comprising an ink container that contains ink, wherein the ink is the water-based ink according to any one of claims 1 to 6.   7. A recording unit comprising an ink storage portion for storing ink and a recording head for discharging ink, wherein the ink is the water-based ink according to claim 1. Characteristic recording unit.   7. The ink-jet recording apparatus including an ink storage unit that stores ink and a recording head for discharging ink, wherein the ink is the water-based ink according to claim 1. An ink jet recording apparatus.

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