JP2010270206A - Water dispersion of colored fine particle, ink for inkjet recording, ink set for inkjet recording, and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water dispersion of colored fine particles, which uses a water-insoluble color material like a pigment, and satisfies characteristics as an ink used in inkjet recording and meets high-speed fixability and higher image quality when the water dispersion is made into an ink. <P>SOLUTION: The water dispersion of colored fine particles includes an aqueous medium, a water-insoluble color material as the colored fine particles, and a plurality of dispersing resins to disperse the colored material in the aqueous medium. Any one of the plurality of dispersing resins is a block copolymer having at least a hydrophobic segment, and a hydrophilic segment composed of a nonionic hydrophilic unit and an ionic hydrophilic unit. When the unit number of the nonionic hydrophilic unit is denoted as B, and the unit number of the ionic hydrophilic unit is denoted as C in the respective dispersing resins, the values of X determined by X=B/(B+C) are different from each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aqueous dispersion of colored fine particles that are excellent in high-speed fixing properties and can form high-quality images when used as inks. The present invention also relates to an ink for ink jet recording using the ink, an ink set for ink jet recording comprising the reaction liquid for reacting the ink and the ink, and an ink jet recording method using the ink set.

  Ink used in conventional ink jet recording generally has water as a main component and contains water-soluble high-boiling solvent such as glycol for the purpose of preventing drying and clogging. However, when recording is performed on plain paper using such inks, sufficient fixing properties cannot be obtained, or non-uniformity estimated to be due to non-uniform distribution of filler and sizing agent on the surface of the recording paper. An image sometimes occurred. In particular, when trying to obtain a color image, the inks of multiple colors are stacked one after another before fixing on the paper, so the colors may blur or mix unevenly at the borders of the different color images. (Hereinafter, this phenomenon is referred to as bleeding), a satisfactory image was not obtained.

  On the other hand, as a means for improving the fixability, Patent Document 1 discloses a method of adding a compound that enhances permeability such as a surfactant into the ink. Patent Document 2 discloses the use of ink mainly composed of a volatile solvent. However, the former method of adding a surfactant or the like to the ink increases the permeability of the ink to the recording paper and improves the fixing property and bleeding of the ink to some extent. It penetrates deeply. For this reason, inconveniences such as a decrease in image density and saturation occur. In addition, spreading of the ink in the lateral direction also occurred, and as a result, problems such as a decrease in edge sharpness and a decrease in resolution occurred. On the other hand, in the case of the latter method using ink mainly composed of a volatile solvent, in addition to the same inconvenience as in the former case, clogging due to evaporation of the solvent at the nozzle portion of the recording head occurs. It was easy to do and was not preferable.

  In order to improve the above-described problems, various methods have been proposed in which a reaction liquid for improving the image is deposited on the recording medium prior to the ejection of the recording ink. Patent Document 3 proposes a method for preventing bleeding by utilizing a reaction between a polyvalent metal ion and a carboxyl group. Furthermore, Patent Document 4 proposes a method for improving bleeding by a reaction with a pigment, a resin emulsion, and a polyvalent metal salt. According to these methods, since the reaction liquid is impregnated into the recording medium and then reacted with the colored ink, bleeding is suppressed to some extent. However, when the color ink has high penetrability with respect to the recording medium, there is a concern that the color developability is deteriorated and the back-through occurs. On the contrary, when the penetrability is low, it takes time to fix the ink. Is concerned.

  In addition, with the recent progress of inkjet technology, the number of nozzles and high-speed printing have advanced, and the demand for ink has been increasing. Then, by increasing the density of the nozzles that discharge ink and supporting high-speed printing, the ink discharged from the nozzles comes into contact with the ink discharged from the adjacent nozzles before penetrating after landing. For this reason, a phenomenon called so-called microbeading that deteriorates the image quality without being able to maintain the shape of the dots becomes a problem.

  Also, considering the development of inkjet printers in the business field, it is considered that further improvement in printing speed will be required, and in response to such demands, high-speed printers that support high-speed printing. Has also been devised. One of the major problems in high-speed printers is the fixability of ink to a recording medium. When the fixing property of ink is poor, the printing on the surface of the previous recording medium is soiled or the subsequent recording is performed in the process in which the subsequent recording medium is laminated on the surface of the previously printed recording medium. For example, the ink of the recording medium discharged first adheres to the back surface of the medium. That is, when a high-speed printer is used, there is a problem that the print quality is deteriorated and the appearance of printed matter may be impaired.

JP 55-65269 A JP-A-55-66976 JP-A-5-202328 JP-A-9-207424

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to provide colored fine particle water that is particularly suitable for the preparation of inks using water-insoluble colorants such as pigments. It is to provide a dispersion. Specifically, it is an object of the present invention to provide an aqueous dispersion of colored fine particles satisfying characteristics for ink jet recording when used as an ink. An object of the present invention is to provide an ink jet recording ink that can cope with high-speed fixing properties and high image quality, an ink set for ink jet recording composed of the ink, and an ink jet recording method using the same.

The first of the present invention is an aqueous dispersion comprising an aqueous medium, a water-insoluble colorant that is a colored fine particle, and a plurality of dispersion resins that disperse the colorant in the aqueous medium. Each of them is a block copolymer having at least a hydrophobic segment and a hydrophilic segment composed of a nonionic hydrophilic unit and an ionic hydrophilic unit, and the non-dispersing resin in each dispersion resin. Colored fine particles characterized in that when the number of unit units of the ionic hydrophilic unit is B and the number of unit units of the ionic hydrophilic unit is C, X values obtained from the following formulas are different from each other: Water dispersion.
(Formula) X = B / (B + C)

  According to a second aspect of the present invention, there is provided an inkjet recording ink comprising at least the aqueous dispersion of colored fine particles and an organic solvent.

  According to a third aspect of the present invention, there is provided an ink set for ink jet recording comprising a combination of at least one ink for ink jet recording and a reaction liquid that reacts with at least one of the inks to aggregate the ink. It is.

  A fourth aspect of the present invention is that the ink set for ink jet recording of the present invention is used, the ink for ink jet recording constituting the ink set and a reaction liquid are applied on the recording medium, and these are reacted on the recording medium. And forming an image by the inkjet recording method.

  According to the present invention, an aqueous dispersion of colored fine particles suitable for preparing an ink using a water-insoluble colorant such as a pigment is provided. In addition, according to the present invention, when an ink is used, an aqueous dispersion of colored fine particles satisfying characteristics for ink jet recording is provided. Furthermore, according to the present invention, there is provided an inkjet recording ink that can cope with high-speed fixability and output of high-density, high-quality printed matter, an inkjet recording ink set composed of the ink, and an inkjet recording method using the ink. Provided.

It is a figure which shows an example of the chemical structure of the block copolymer used for this invention. FIG. 2 is a schematic perspective view illustrating a main part of an example of a printer on which a recording head can be mounted. It is a schematic perspective view showing an example of a cartridge provided with a recording head.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention. In the description of the following specification, “aqueous dispersion of colored fine particles” is “water dispersion”, “ink for inkjet recording” is “ink”, and “ink set for inkjet recording” is “ink set”. May be referred to as "."

<Colored fine particle aqueous dispersion and ink>
(Water-insoluble colorant)
As the water-insoluble colorant used in the present invention, a pigment is used. The pigment may be either an organic pigment or an inorganic pigment, and the pigment used in the aqueous dispersion or ink is preferably a black pigment, cyan, Three primary color pigments of magenta and yellow can be used. Color pigments other than those described above, colorless or light color pigments, or metallic luster pigments may be used. In the present invention, commercially available pigments conventionally used in ink jet inks may be used, or newly synthesized pigments may be used. Moreover, you may use together with dye.

  In the aqueous dispersion or ink of the present invention, a pigment that is self-dispersible in water can also be used. As pigments that can be self-dispersed in water, there are pigments that utilize the steric hindrance effect in which a polymer is adsorbed on the pigment surface, and pigments that utilize electrostatic repulsion. Examples of commercially available products include CAB-0-JET200, CAB-0-JET300 (manufactured by Cabot Corporation), Microjet Black CW-1 (manufactured by Orient Chemical Co., Ltd.), and the like.

  In the present invention, the content of the pigment is preferably an amount that is in the range of 0.1% by mass or more and 30% by mass or less with respect to the total mass of the ink when an aqueous dispersion is used as the ink. When the pigment content is less than 0.1% by mass, a sufficient image density cannot be obtained, and when it exceeds 30% by mass, the pigments aggregate and cannot be dispersed. A more preferable range is 0.5 mass% or more and 10 mass% or less. More preferably, it is the range of 0.7 mass% or more and 7 mass% or less. In the present invention, the average particle diameter of the pigment is preferably in the range of 50 nm to 200 nm, and preferably 100 nm or less in order to obtain better image quality. The average particle diameter of the pigment was measured using FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.).

(Dispersed resin)
In the present invention, a plurality of dispersion resins for dispersing pigment particles in an aqueous medium are used, and these are characterized by having the following configuration. First, all of the plurality of dispersion resins are required to be a block copolymer having at least a hydrophobic segment and a hydrophilic segment composed of a nonionic hydrophilic unit and an ionic hydrophilic unit. Further, in each dispersion resin, when the number of unit units of the nonionic hydrophilic unit is B and the number of unit units of the ionic hydrophilic unit is C, it is obtained from X = B / (B + C). A plurality of different values of X are used. These will be described later. The weight average molecular weight of each dispersed resin is preferably 1,000 or more and 30,000 or less. Furthermore, Preferably, it is the range of 3,000 or more and 15,000 or less. Examples of the dispersion resin include a block copolymer composed of at least two monomers selected from the monomers listed below (of which at least one is a hydrophilic monomer), or a salt thereof. Is mentioned. Monomers 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 derivatives , Fumaric acid and its derivatives. As the dispersion resin, a triblock copolymer containing a polyvinyl ether structure described later as a repeating unit structure is preferably used. These resins are soluble in an aqueous solution in which a base is dissolved, and are alkali-soluble resins. Note that the content of these dispersion resins is an amount that is in the range of 0.1% by mass to 10% by mass with respect to the total mass of the ink when an aqueous dispersion is used as the ink. preferable.

  The block copolymer for dispersing the water-insoluble colorant used in the present invention has at least a hydrophobic segment and a hydrophilic segment, and the hydrophilic segment further includes a nonionic hydrophilic unit and an ion. Hydrophilic unit. In the present invention, when the number of unit units of the nonionic hydrophilic unit is B and the number of unit units of the ionic hydrophilic unit is C, X obtained from X = B / (B + C) A plurality of dispersed resins having different values are used. That is, in the present invention, a plurality of block copolymers are used as a dispersion resin for dispersing a water-insoluble colorant in an aqueous medium, and the proportion of nonionic hydrophilic units in the hydrophilic segments constituting them However, a different thing is used for each.

  FIG. 1 is a diagram showing an example of the chemical structure of a block copolymer used in the present invention. In the block copolymer illustrated in FIG. 1, a hydrophobic segment (A segment), a nonionic hydrophilic unit (B segment), and an ionic hydrophilic unit (C segment) are arranged in this order. It has a structure. In FIG. 1, “-b-” is a symbol indicating that it is a block copolymer, and “A”, “B”, and “C” are the number of unit units in each segment, respectively. In the present invention, in the dispersion resin having such a structure, the ratio of the number of unit units B of the nonionic hydrophilic unit to the total number of unit units in the hydrophilic segment (that is, (B + C)) is different. A plurality of dispersion resins are used.

  Furthermore, in this invention, it is preferable that the difference of the value of X in the some dispersion resin to be used is the range of 0.17 or more and 0.4 or less. In the present invention, at least the dispersion resin having a value of X in the range of 0.5 to 0.73 and the dispersion resin having a value of X in the range of 0.33 to 0.5 are included. It is preferable that

  In contrast to the above configuration, the present inventors have used a block copolymer consisting of a hydrophobic segment and a hydrophilic segment as a dispersion resin, but with an ink in which a water-insoluble colorant is dispersed using a single resin, It has been found that there are the following problems depending on the structure. First, if the proportion of the nonionic hydrophilic unit in the hydrophilic segment is small, the steric hindrance effect is insufficient, resulting in unstable dispersion or problems when ejecting with an inkjet head. There is. On the other hand, when the proportion of the nonionic hydrophilic unit in the hydrophilic segment is large, bleeding does not occur even when the ink lands on the recording medium, and bleeding with other colors may occur. In addition, since the water-insoluble colorant penetrates into the recording medium together with the solvent, there may be a problem that OD (optical density) is difficult to occur.

  Therefore, in the present invention, in order to solve these problems, a block resin composed of a hydrophobic segment and a hydrophilic segment, each having a different X value, is dispersed in a dispersion resin for dispersing a water-insoluble colorant in an aqueous medium. A plurality of polymers are used. As a result, by adding an organic solvent to the obtained aqueous dispersion of colored fine particles, it becomes possible to prepare an ink without deteriorating the ejection characteristics and bleed characteristics. In addition, it was confirmed that the OD of the formed recorded image was significantly improved as compared with the image formed with the ink using a single dispersion resin. In particular, when the ink and the reaction liquid are used and applied to a recording method in which these are reacted on a recording medium to promote aggregation, the above-described effect is remarkably exhibited. The reason for this is not clear, but in the present invention, since the dispersion resin for dispersing colored fine particles having different characteristics described above is mixed in the aqueous dispersion (ink), the aggregation of the ink by the reaction liquid is caused. This is thought to be promoted.

  Specific examples of the block copolymer used in the present invention include the following known block copolymers. That is, acrylic, methacrylic block copolymers, polystyrene and other addition polymerization or condensation polymerization block copolymers, block copolymers having polyoxyethylene and polyoxyalkylene blocks, and the like. The block copolymer used in the present invention preferably contains a polyvinyl ether structure as a repeating unit structure. Moreover, it is preferable that the nonionic hydrophilic unit in the block copolymer used for this invention contains an ethylene oxide structure.

  Specific examples of the repeating unit of the ionic hydrophilic unit (C segment) include a repeating unit represented by the following general formula (1).

（一般式（１）中、Ｒ⁰は−Ｘ−(ＣＯＯＨ)_r、−Ｘ−(ＣＯＯ−Ｍ)_r又は−Ｘ²−(ＣＯＯ)₂−Ｍ²を表す。Ｘは炭素数１乃至２０までの直鎖状、分岐状又は環状のアルカンジイル若しくはアルカントリイル基、又は−(ＣＨ（Ｒ⁵)−ＣＨ(Ｒ⁶)−Ｏ)_p−(ＣＨ₂)_m−ＣＨ_3-r−若しくは−(ＣＨ₂)_m−(Ｏ)_n−(ＣＨ₂)_q−ＣＨ_3-r−。又は、それらのメチレン基の少なくとも一つがカルボニル基又は芳香環構造で置換された構造を表す。ｒは１乃至２を表す。Ｘ²はＸのうちｒが２の基を表す。ｐは１乃至１８までの整数を表す。ｍは０乃至３５までの整数を表す。ｎは１又は０を表す。ｑは０乃至１７の整数を表す。Ｍは１価のカチオンを表す。Ｍ²は２価のカチオンを表す。Ｒ⁵及びＲ⁶はアルキル基を表す。Ｒ⁵、Ｒ⁶は同じでも又は異なっていてもよい。）

(In the general formula (1), R ⁰ represents —X— (COOH) _r , —X— (COO—M) _r or —X ² — (COO) ₂ —M ² , where X represents 1 to 20 carbon atoms. to straight, branched or cyclic alkanediyl or alkanetriyl group, or ^{- (CH (R 5) -CH} (R 6) -O) p - (CH 2) m -CH 3-r - or _{- (CH 2) m - (} O) n - (CH 2) q -CH 3-r -. or, .r representing at least one is substituted with a carbonyl group or an aromatic ring structure the structure of those of the methylene groups is 1 to 2 X ² represents a group in which r is 2 in X. p represents an integer from 1 to 18. m represents an integer from 0 to 35. n represents 1 or 0. q is .M ² .M is representative of a monovalent cation represents an integer of 0 to 17 represents .R ^5, R ⁶ are identical or different and are .R ⁵ and R ⁶ represents a divalent cation alkyl group There may be.)

  Specific examples of the repeating unit structure represented by the general formula (1) constituting the ionic hydrophilic unit (C segment) are given below.

  Furthermore, the specific structure of the repeating unit of the hydrophobic segment (A segment) or nonionic hydrophilic unit (B segment) includes a repeating unit represented by the following general formula (2).

（一般式（２）中、Ｒ¹は炭素数１乃至１８までの直鎖状、分岐状又は環状のアルキル基、−Ｐｈ、−Ｐｙｒ、−Ｐｈ−Ｐｈ、−Ｐｈ−Ｐｙｒ、−Ｎｐ、−(ＣＨ(Ｒ⁵)−ＣＨ(Ｒ⁶)−Ｏ)_p−Ｒ⁷及び−(ＣＨ₂)_m−(Ｏ)_n−Ｒ⁷から選ばれる基である。また、該基における、芳香環中の炭素原子に結合している水素原子は炭素数１乃至４の直鎖状又は分岐状のアルキル基と、また芳香環中の炭素原子は窒素原子とそれぞれ置換していてもよい基を表す。ｐは１乃至１８の整数、ｍは１乃至３６の整数、ｎは０又は１を表す。Ｒ⁵及びＲ⁶はそれぞれ独立に水素原子若しくは−ＣＨ₃を表す。Ｒ⁵及びＲ⁶が複数ある場合はそれぞれ同じでも異なっていてもよい。Ｒ⁷は水素原子、炭素数１乃至１８までの直鎖状、分岐状又は環状のアルキル基、−Ｐｈ、−Ｐｙｒ、−Ｐｈ−Ｐｈ、−Ｐｈ−Ｐｙｒ、−Ｎｐ、−ＣＨＯ、−ＣＨ₂ＣＨＯ、−ＣＯ−ＣＨ＝ＣＨ₂及び−ＣＯ−Ｃ(ＣＨ₃)＝ＣＨ₂から選ばれる基である。また、Ｒ⁷が水素原子以外である場合、Ｒ⁷中の炭素原子に結合している水素原子は炭素数１乃至４の直鎖状又は分岐状のアルキル基又は−Ｆ、−Ｃｌ、−Ｂｒと、また芳香環中の炭素原子は窒素原子とそれぞれ置換することができる。Ｐｈはフェニル基又はフェニレン基、Ｐｙｒはピリジル基、Ｎｐはナフチル基を表す。）

(In the general formula (2), R ¹ is a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, -Ph, -Pyr, -Ph-Ph, -Ph-Pyr, -Np,- A group selected from (CH (R ⁵ ) —CH (R ⁶ ) —O) _p —R ⁷ and — (CH ₂ ) _m — (O) _n —R ⁷ . The hydrogen atom bonded to the carbon atom represents a linear or branched alkyl group having 1 to 4 carbon atoms, and the carbon atom in the aromatic ring represents a group that may be substituted with a nitrogen atom. p is an integer of 1 to 18, m is an integer of 1 to 36, and n is 0 or 1. R ⁵ and R ⁶ each independently represents a hydrogen atom or —CH ₃ , and there are a plurality of R ⁵ and R ^6. R ⁷ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, —Ph. , Is a group selected -Pyr, -Ph-Ph, -Ph- Pyr, -Np, -CHO, -CH 2 CHO, -CO-CH = CH 2 and -CO-C (CH ₃₎ from = CH ₂ When R ⁷ is other than a hydrogen atom, the hydrogen atom bonded to the carbon atom in R ⁷ is a linear or branched alkyl group having 1 to 4 carbon atoms or —F, —Cl, — Br and carbon atoms in the aromatic ring can be substituted with nitrogen atoms, Ph represents a phenyl group or a phenylene group, Pyr represents a pyridyl group, and Np represents a naphthyl group.)

  Specific examples of the repeating unit structure represented by the general formula (2) constituting the hydrophobic segment (A segment) include those described below.

  Specific examples of the unit structure represented by the general formula (2) constituting the nonionic hydrophilic unit (B segment) include those described below.

  Each block segment (unit) of the block copolymer used in the present invention may be composed of a single repeating unit or may be composed of a plurality of repeating unit structures. Examples of the block segment composed of a plurality of repeating units include a random copolymer and a gradient copolymer whose composition ratio gradually changes. The block copolymer used in the present invention may be a polymer in which the block copolymer structure is graft-bonded to another polymer.

  The content of the repeating unit structure represented by the general formula (1) or the general formula (2) contained in the block copolymer is 0.01 mol% or more and 99 mol% or less with respect to the entire block copolymer, preferably Is preferably in the range of 1 mol% to 90 mol%. If it is less than 0.01 mol%, the polymer interaction that the ionic functional group, hydrophobic functional group, or nonionic hydrophilic group should work may be insufficient, and if it exceeds 99 mol%, the interaction will work too much. The function may be insufficient. The number average molecular weight (Mn) of the block copolymer used in the present invention is in the range of 200 or more and 10,000,000 or less, and the range preferably used is 1,000 or more and 1,000,000 or less. When it exceeds 10,000,000, the entanglement within the polymer chain and between the polymer chains becomes excessive, and it is difficult to disperse in the solvent. If it is less than 200, the steric effect as a polymer may be difficult to obtain due to the low molecular weight. The preferred number of unit units for each block segment is 3 or more and 10,000 or less. More preferably, it is 5 or more and 5,000 or less. More preferably, it is 10 or more and 4,000 or less. In the present invention, the number of unit units means the number of polymerized monomers constituting the hydrophobic segment, the nonionic hydrophilic unit and the ionic hydrophilic unit, respectively.

  In addition, the method for synthesizing the block copolymer which is a dispersion resin is not particularly limited, and various methods can be used. For example, a method using living cationic polymerization by Aoshima et al. (Polymer Bulletin, Vol. 15, 1986, page 417, JP-A-11-322942, JP-A-11-322866) can be used.

(Method for producing aqueous dispersion of colored fine particles)
The method for producing an aqueous dispersion of colored fine particles of the present invention can be easily obtained by a usual method using a water-insoluble colorant and a dispersion resin as raw materials. At that time, as described below, a water dispersion is prepared by dispersing a water-insoluble coloring material in an aqueous medium using one type of dispersion resin, and an aqueous dispersion is similarly prepared using a different dispersion resin. Thereafter, it is preferable to prepare a water dispersion of colored fine particles by mixing a plurality of these.

  As a specific method for preparing each aqueous dispersion, a physical treatment such as a sand mill, a bead mill, or a kneader is performed in order that the dispersion resin is physically adsorbed on the water-insoluble colorant and stably dispersed in an aqueous medium. The method can be used. In addition, a method in which a water-insoluble colorant and a dispersion resin are allowed to coexist in an aqueous medium, and the solubility of the dispersion resin is reduced in the aqueous medium and deposited on the surface of the water-insoluble colorant. In addition, when the water-insoluble color material is once dissolved and converted into the water-insoluble color material again, a chemical treatment method such as a method of making a dispersion state with a dispersion resin can be used. In the present invention, an appropriate method may be selected from the methods listed above. In the aqueous dispersion of the present invention, P / B (pigment concentration / dispersion resin concentration) is preferably in the range of 0.5 to 5.0.

(Aqueous medium)
The aqueous medium suitably used for the aqueous dispersion and ink of the present invention is a mixed solvent of water, a buffer solution and a water-soluble organic solvent, and water and water contained in the buffer solution contain various ions. It is preferable to use ion-exchanged water (deionized water) instead of ordinary water. Further, the water-soluble organic solvent used in the present invention is not particularly limited as long as it is soluble in water, but preferably, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, Polyhydric alcohols such as butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, and trimethylolpropane are preferably used. Other alkyl ethers of polyhydric alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, urea, 2-pyrrolidone N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, triethanolamine and the like.

  In the present invention, the content of the water-soluble organic solvent is preferably an amount that is in the range of 3% by mass to 50% by mass with respect to the total mass of the ink when an aqueous dispersion is used as the ink. . The water content is preferably 10% by mass or more and 90% by mass or less with respect to the total mass of the ink when the aqueous dispersion is used as ink.

(Other ingredients)
The ink of the present invention further contains other components, for example, a surfactant, an antifoaming agent, an antiseptic, an antifungal agent, etc., as necessary, in order to obtain an ink having a desired physical property value. Also good.

<Ink set>
(Reaction solution)
The ink set of the present invention uses the aqueous dispersion of colored fine particles of the present invention and reacts with at least one of the inks for ink jet recording prepared as described above and at least one of the inks. It has a combination with the reaction liquid to be agglomerated. At this time, a reaction solution containing a polyvalent metal ion is preferably used. The reaction solution may be transparent or colored. Further, the colored reaction liquid may contribute to image formation. As the polyvalent metal ions used in the reaction solution, Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ³⁺ , Ba ²⁺ , Al ³⁺ , Fe ³⁺ , Cr ³⁺ , Co ²⁺ , Fe ²⁺ , La ²⁺ , Nd ³⁺ and Y ³⁺ . These cations may be contained in the reaction solution as a salt. Representative and preferred anions that can be combined with the above cations to form salts include, for example, Cl ⁻ , NO ₃ ⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , and CH ₃ COO. ^-, SO ₃ ^- there are not intended to be limited thereto. The concentration of the polyvalent metal salt in the reaction solution is preferably in the range of 0.01% by mass to 10% by mass. A more preferable range of the polyvalent metal salt concentration is 1% by mass or more and 5% by mass or less. A more preferable range of the polyvalent metal salt concentration is 1% by mass or more and 3% by mass or less.

  As the aqueous medium used for the reaction solution, the same ones as described above can be used. The content of the aqueous medium in the reaction solution is not particularly limited, but is preferably in the range of 30% by mass to 95% by mass with respect to the total mass of the reaction solution. In addition, the reaction solution may further contain components such as a surfactant, an antifoaming agent, a preservative, and an antifungal agent, if necessary.

<Inkjet recording method>
In the ink jet recording method of the present invention, the image of the present invention is formed by applying the ink of the present invention and a reaction liquid onto a recording medium, reacting them, and aggregating the ink. At that time, the reaction liquid may be applied by a roller or the like, or may be discharged from an ink jet head and applied to the landing position of the ink on the reaction side. And in this invention, it is preferable to have the process by which a reaction liquid is provided to a recording medium prior to application | coating of an ink.

  As described above, since the reaction liquid and the ink are reacted on the recording medium to form an image, it is preferable to control the permeability of each ink and the reaction liquid on the recording medium. Specifically, in the ink set, it is preferable to make the surface tensions of the reaction liquid and the ink different. Since the ink and the reaction liquid are reacted on the paper surface, it is preferable to reduce the permeability of the reaction liquid applied first and to increase the permeability of the ink applied later. That is, the surface tension of the reaction liquid is preferably higher than the surface tension of the ink. The surface tension of the ink and the reaction liquid is adjusted by the type and amount of the surfactant. In the reaction solution, the surface tension is adjusted to about 30 mN / m or more and 50 mN / m or less. More preferably, it is about 40 mN / m or more and 50 mN / m or less. On the other hand, the surface tension of the ink is adjusted to about 25 mN / m or more and 40 mN / m or less. More preferably, it is about 30 mN / m or more and 35 mN / m or less.

  As the ink ejection method, any known method such as a piezo method can be adopted. In the most preferable mode, a method in which bubbles are generated in ink using thermal energy and ink is ejected by the pressure of the bubbles is preferably used because the density of nozzles ejected by ink can be increased.

<Inkjet image recording device>
Next, an ink jet image recording apparatus suitable for the ink jet recording method of the present invention will be described.
FIG. 2 is a schematic perspective view showing a main part of an example of a liquid ejection head as an ejection type inkjet head (recording head) that communicates air bubbles with the atmosphere during ejection and an inkjet printer as an inkjet image recording apparatus using the head. is there.

  In FIG. 2, the ink jet printer includes a conveyance device 1030 that intermittently conveys a sheet 1028 as a recording medium provided in the casing 1008 along the longitudinal direction in a direction indicated by an arrow P in the drawing. Yes. Further, a recording unit 1010 that reciprocates substantially in parallel with the guide shaft 1014 in an arrow S direction substantially orthogonal to the conveyance direction P of the paper 1028 by the conveying device 1030, and a drive unit that reciprocates the recording unit 1010. The moving drive unit 1006 is included.

  The conveying device 1030 includes a pair of roller units 1022a and 1022b that are arranged to face each other substantially in parallel, a pair of roller units 1024a and 1024b, and a drive unit 1020 for driving these roller units. Yes. With this configuration, when the driving unit 1020 of the transport device 1030 is activated, the paper 1028 is sandwiched between the roller units 1022a and 1022b and the roller units 1024a and 1024b and transported intermittently in the direction of arrow P. Will be. The movement drive unit 1006 includes a pulley 1026a and a belt 1016 wound around a pulley 1026a and a pulley 1026b that are arranged to face each other with a predetermined interval. The motor 1018 is configured to drive a belt 1016 that is arranged substantially parallel to the roller unit 1022a and the roller unit 1022b and connected to the carriage member 1010a of the recording unit 1010 in the forward direction and the reverse direction.

  When the motor 1018 is activated and the belt 1016 rotates in the direction of arrow R shown in the drawing, the carriage member 1010a of the recording unit 1010 is moved in the direction of arrow S by a predetermined amount of movement. When the motor 1018 is activated and the belt 1016 rotates in the direction opposite to the arrow R direction shown in the drawing, the carriage member 1010a of the recording unit 1010 moves in a predetermined direction in the direction opposite to the arrow S direction. It will be moved by the amount. Further, a recovery unit 1026 for performing an ejection recovery process of the recording unit 1010 is opposed to the ink ejection port array of the recording unit 1010 at one end of the movement driving unit 1006 at a position that is the home position of the carriage member 1010a. Is provided.

  The recording unit 1010 includes inkjet cartridges 1012Y, 1012M, 1012C, and 1012B that are detachably attached to the carriage member 1010a for each color, for example, yellow, magenta, cyan, and black. In the following description, the ink jet cartridge may be simply referred to as a cartridge. The effect of the ink according to the present invention is not limited to a specific color. For example, it is also preferable that two or more selected from the yellow, magenta, cyan, and black inks are the ink according to the present invention. This is one of the embodiments.

  FIG. 3 shows an example of an ink jet cartridge that can be mounted on the above-described ink jet recording apparatus. A cartridge 1012 shown in FIG. 3 is of a serial type, and the main part is composed of an inkjet head 100 and a liquid tank 1001 that stores a liquid such as ink.

  The ink jet head 100 is formed with a large number of ejection ports 832 for ejecting a liquid, and a liquid such as ink is supplied from a liquid tank 1001 through a liquid supply passage (not shown). (Shown). In the cartridge 1012 shown in FIG. 3, the ink jet head 100 and the liquid tank 1001 are integrally formed so that liquid can be supplied into the liquid tank 1001 as necessary. Further, a structure in which the liquid tank 1001 is connected to the liquid discharge head 100 in a replaceable manner may be adopted.

  Next, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these Examples. In the following description, “%” is based on mass unless otherwise specified.

<Synthesis of block copolymer>
A block copolymer having a hydrophobic segment as a unit structure (20) or a unit structure (28), a nonionic hydrophilic segment as a unit structure (32), and an ionic hydrophilic segment as a unit structure (11) as an aluminum catalyst A total of 6 types were synthesized by living cationic polymerization using

  Specifically, each block copolymer was synthesized by the following method. First, after the inside of the glass container with the three-way cock attached was replaced with nitrogen, the adsorbed water was removed by heating to 250 ° C. in a nitrogen gas atmosphere. After returning the system to room temperature, the monomer of the A segment was added to 16 mmol of ethyl acetate, 0.1 mmol of 1-isobutoxyethyl acetate, and 11 ml of toluene, and the reaction system was cooled. When the system temperature reached 0 ° C., 0.2 mmol of ethylaluminum sesquichloride (an equimolar mixture of diethylaluminum chloride and ethylaluminum dichloride) was added to initiate polymerization. The molecular weight was monitored in a time-sharing manner using molecular sieve column chromatography (GPC) to confirm the completion of polymerization of the A segment.

  The B segment monomer was then added and polymerization continued. After confirming the completion of the polymerization of the B segment by monitoring using GPC, a toluene solution of the C segment component was added to continue the polymerization. After 20 hours, the polymerization reaction was stopped. The polymerization reaction was stopped by adding 0.3% ammonia / methanol aqueous solution to the system. The reaction mixture solution was diluted with dichloromethane and washed 3 times with 0.6M hydrochloric acid and then 3 times with distilled water. The organic phase obtained was concentrated and dried with an evaporator, and then vacuum-dried, and then repeatedly dialyzed in a methanol solvent using a cellulose semipermeable membrane to remove the monomeric compound, and the target product, tri A block polymer was obtained.

  Furthermore, the triblock polymer obtained here was hydrolyzed in a mixed solution of dimethylformamide and sodium hydroxide, and the C segment component was hydrolyzed to obtain a sodium salt triblock polymer. The compound was identified using NMR and GPC. Furthermore, the triblock polymer in which the C segment component became a free carboxylic acid was obtained by neutralization with 0.1N hydrochloric acid in an aqueous dispersion. The compound was identified using NMR and GPC. Table 1 shows data on the number of polymerizations (number of unit units), number average molecular weight Mn, and molecular weight distribution Mw / Mn for each segment of the block copolymer produced this time.

<Preparation of aqueous dispersion of colored fine particles>
(Black pigment aqueous dispersion)
Each block copolymer obtained above was used as a dispersion resin, and an aqueous dispersion of Black pigment was prepared by dispersing the pigment with the resin. Specifically, it was prepared as follows. First, 300 mL Kolben equipped with a mechanical stirrer is placed in a tank of an ultrasonic generator, and 12.0 g of the block polymer obtained above, 12.0 g of carbon black, and 120 mL of tetrahydrofuran are added to the surface of the pigment. Mix well until wet with solvent. Next, phase inversion was performed by dropping and injecting an aqueous alkali solution containing KOH so that the neutralization rate of the block polymer was 100%. Thereafter, premixing was performed for 30 minutes, and dispersion was performed using Nanomizer YSNM-2000AR (manufactured by Yoshida Kikai Kogyo Co., Ltd.) until the average particle size of the pigment became 100 nm or less. Using a rotary evaporator, tetrahydrofuran is distilled off from this dispersion, and the concentration is adjusted to obtain a pigment pigment (P) of 6%, a dispersion resin concentration (B) of 6%, and a black pigment water of P / B = 1.0. A dispersion was obtained. The carbon black used above is Monarch 880 (manufactured by Cabot Special Chemicals).

<Example 1>
A mass ratio of 1: 1 of an aqueous dispersion of Black pigment prepared by the above method using BP1 shown in Table 1 and an aqueous dispersion of Black pigment prepared by the above method using BP2 shown in Table 1 To obtain an aqueous dispersion of colored fine particles of Example 1.

<Example 2>
A mass ratio of 1: 1 of an aqueous dispersion of Black pigment prepared by the above method using BP1 shown in Table 1 and an aqueous dispersion of Black pigment prepared by the above method using BP3 shown in Table 1 To obtain an aqueous dispersion of colored fine particles of Example 2.

<Example 3>
A mass ratio of 1: 1 of an aqueous dispersion of black pigment prepared by the above method using BP4 shown in Table 1 and an aqueous dispersion of black pigment prepared by the above method using BP5 shown in Table 1 To obtain an aqueous dispersion of colored fine particles of Example 3.

<Example 4>
A mass ratio of 1: 1 of an aqueous dispersion of Black pigment prepared by the above method using BP5 shown in Table 1 and an aqueous dispersion of Black pigment prepared by the above method using BP6 shown in Table 1 To obtain an aqueous dispersion of colored fine particles of Example 4.

<Example 5>
A mass ratio of 1: 1 of an aqueous dispersion of Black pigment prepared by the above method using BP2 shown in Table 1 and an aqueous dispersion of Black pigment prepared by the above method using BP6 shown in Table 1 To obtain an aqueous dispersion of colored fine particles of Example 5.

<Comparative Examples 1-6>
Black pigment aqueous dispersions prepared by the above method using B1 to B6 shown in Table 1 were used as aqueous dispersions of colored fine particles of Comparative Examples 1 to 6, respectively.

<Preparation of ink>
Glycerin, diethylene glycol, trimethylolpropane, and acetylenol EH (manufactured by Kawaken Fine Chemical Co., Ltd.) were added to the aqueous dispersions of the colored fine particles obtained in Examples and Comparative Examples obtained above with the compositions shown in Tables 2 and 3 below. An ink was prepared. The pH of the ink was adjusted to 9.5 using KOH for all the inks. The amount of ion-exchanged water in the ink composition was “remaining”, which means that the amount of ink composition was adjusted with ion-exchanged water so that the total amount of the ink composition was 100%.

<Preparation of reaction solution>
Using Mg nitrate, glycerin, diethylene glycol, trimethylolpropane, acetylenol EH (manufactured by Kawaken Fine Chemical Co., Ltd.) and making the total amount to 100% with ion-exchanged water, a reaction solution was prepared with the composition shown below. . Further, the pH of the reaction solution is adjusted to 7.0.
-Mg nitrate 2.5%
・ Glycerin 7.0%
・ Diethylene glycol 5.0%
・ Trimethylolpropane 7.0%
・ Acetylenol EH 0.2%
・ Ion exchange water remaining

<Preparation of ink set>
Each ink obtained above was combined with the reaction liquid obtained above to prepare an ink set.

<Evaluation of image>
Images were formed using each of the prepared ink sets, and the obtained images were evaluated for color unevenness stability, bleeding, and OD as follows. Evaluation is carried out by mounting the black ink obtained in the above, the reaction liquid, and the dye yellow ink (BCI-6Y, manufactured by Canon Inc.) on an ink jet printer BJF-930 (manufactured by Canon Inc.), and each of the recording media is subjected to predetermined conditions. The images obtained by printing with the method were performed. Professional photo paper PR101 (manufactured by Canon Inc.) was used as the recording medium. Note that printing by the inkjet printer BJF-930 is high-speed printing of 10 seconds per A4 size sheet.

(Color unevenness evaluation)
First, 100% duty solid printing was performed on 100 A4 size recording media using each Black ink. Thereafter, a solid patch (5 × 5 cm) was printed using Black ink, and the obtained solid patch image was checked for the presence or absence of color unevenness. Color unevenness was evaluated based on the following criteria. The obtained evaluation results are shown in Table 4.
Evaluation A: Color unevenness is not visible.
Evaluation B: Some color unevenness occurs.
Evaluation C: Color unevenness occurs remarkably.
In this evaluation, the color unevenness generated in the print samples as the results corresponding to the evaluations B and C was a streaky unevenness.

(Bleeding evaluation)
Adjacent to the yellow printing portion formed by yellow ink (BCI-6Y, manufactured by Canon Inc.), each of the black inks obtained above was printed with a grid pattern of 5 mm with a line width of 5 mm at 100% duty. The degree of bleeding and color mixing at the boundary between Black and Yellow was evaluated from the obtained Black print portion and Yellow print portion. In addition, the reaction liquid containing 2.5% of Mg nitrate obtained in the above is previously printed on the Black printing portion in the same pattern as the Black ink printing pattern at 25% duty. Bleeding was evaluated based on the following criteria. The evaluation results are shown in Table 4.
Evaluation A: The boundary between other colors is clear at each location, and no blur or color mixing is observed at the boundary.
Evaluation B: Some blurring and color mixing are observed at the boundary.
Evaluation C: Bleeding at the boundary portion and color mixing can be remarkably confirmed.

(OD evaluation)
The printed image was printed in the same pattern as that used in bleeding evaluation under the condition of the presence or absence of the reaction solution, and the OD of the Black printing portion was measured using RD-19 (manufactured by Gretag Macbeth). The measurement results are shown in Table 4.

  From the above evaluation results, the images using the inks of the examples of the present invention are all deteriorated in the ejection characteristics as compared with the images using the inks of the comparative examples in which the pigment is dispersed with one kind of polymer. It was shown that the OD was improved without deteriorating the color unevenness and bleed characteristics associated with. In particular, in the case of an image formed using a reaction liquid together with ink, the effect is remarkable, high color developability is exhibited, and high fixability is exhibited despite high-speed printing.

Claims (10)

An aqueous dispersion comprising an aqueous medium, a water-insoluble colorant that is a colored fine particle, and a plurality of dispersion resins that disperse the colorant in the aqueous medium, each of the plurality of dispersion resins being at least hydrophobic A block copolymer having a segment and a hydrophilic segment composed of a nonionic hydrophilic unit and an ionic hydrophilic unit, and the nonionic hydrophilic unit in each dispersion resin. An aqueous dispersion of colored fine particles, wherein the number of unit units is B and the number of unit units of the ionic hydrophilic unit is C, the values of X obtained from the following formulas are different from each other.
(Formula) X = B / (B + C)   The aqueous dispersion of colored fine particles according to claim 1, wherein a plurality of aqueous dispersions comprising an aqueous medium, a water-insoluble coloring material that is colored fine particles, and a dispersion resin that disperses the coloring material in the aqueous medium are mixed. object.   The aqueous dispersion of colored fine particles according to claim 1 or 2, wherein the nonionic hydrophilic unit includes an ethylene oxide structure.   The aqueous dispersion of colored fine particles according to any one of claims 1 to 3, wherein the dispersion resin contains a polyvinyl ether structure as a repeating unit structure.   An ink for ink-jet recording, comprising at least the aqueous dispersion of colored fine particles according to any one of claims 1 to 4 and an organic solvent.   An ink set for ink jet recording comprising a combination of at least one ink for ink jet recording according to claim 5 and a reaction liquid that reacts with at least one of the inks to aggregate the ink.   The ink set for inkjet recording according to claim 6, wherein the reaction liquid contains a polyvalent metal ion. The polyvalent metal ions are Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ³⁺ , Ba ²⁺ , Al ³⁺ , Fe ³⁺ , Cr ³⁺ , Co ²⁺ , Fe ^2+. The ink set for inkjet recording according to claim 7, wherein the ink set is at least one selected from the group consisting of La ²⁺ , Nd ^3+, and Y ³⁺ .   The ink set for ink jet recording according to any one of claims 6 to 8, and the ink for ink jet recording and the reaction liquid constituting the ink set are applied on a recording medium, and these are applied on the recording medium. An ink jet recording method comprising forming an image by reaction.   The inkjet recording method according to claim 9, further comprising a step of applying the reaction liquid to a recording medium prior to application of the ink.

Images