JP2010095608A - Pigment ink, method for producing pigment ink and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide pigment ink which can be used in inkjet recording, exhibits high dispersion stability and ensures good ejection, and from which a high-quality image having high recording density and substantially free of bleeding is obtained even in recording on plain paper, and to provide a method for producing pigment ink by which the above pigment ink having excellent properties can easily be obtained and an inkjet recording method using the pigment ink having excellent properties. <P>SOLUTION: The pigment ink comprises an aqueous medium, a pigment and two or more block copolymers each having a hydrophobic segment and a hydrophilic segment in its structure, wherein the structures of hydrophobic segments which the respective block copolymers have are different from each other. The method for producing the pigment ink and the inkjet recording method are also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pigment ink, a pigment ink manufacturing method, and an ink jet recording method. More specifically, a pigment ink having excellent ink dispersion stability, good ejection characteristics, high OD (optical density) when printed on a recording medium, and good scratch resistance, and method for producing pigment ink And an inkjet recording method.

  Conventional inks used in ink jet recording methods are generally water-based inks containing an aqueous medium containing water as a main component and a water-soluble high-boiling solvent such as glycol for the purpose of preventing drying and clogging. there were. However, when recording is performed on recording paper such as plain paper using such water-based ink, sufficient fixing properties cannot be obtained, or due to uneven distribution of filler and sizing agent on the surface of the recording paper. An estimated nonuniform image may occur. In particular, when a full-color image is obtained by the ink jet recording method, the next ink is applied before the applied ink is fixed on the recording paper, and a plurality of colors of ink are superimposed one after another. For this reason, colors may be blurred or mixed non-uniformly at the boundary between different color ink images (this phenomenon is referred to as bleeding), and a satisfactory image may not be obtained.

  On the other hand, as a means for improving the fixability of ink, there is a proposal for a method of adding a compound that enhances permeability such as a surfactant into the ink (see Patent Document 1). Further, a method using an ink composed mainly of a volatile solvent has been proposed (see Patent Document 2). According to the former method of adding a compound that enhances permeability such as a surfactant into the ink, the permeability of the ink to the recording paper can be increased, and the ink fixing property and the suppression of bleeding are improved to some extent. Can be made. However, in this method, the color material in the ink also penetrates deep into the recording paper, which causes another problem that the density and saturation of the image are lowered. Further, in this method, the ink spreads in the lateral direction, and as a result, there is a problem that the sharpness of the edge of the image is lowered and the resolution is lowered. On the other hand, in the case of the latter method using ink mainly composed of a volatile solvent, in addition to the same disadvantages as in the former method, clogging due to evaporation of the solvent at the nozzle portion of the recording head occurs. There is also a problem that the ink jet recording characteristics are poor.

  In order to improve the above-mentioned problems, various methods have been proposed in which a reaction liquid for the purpose of improving the image separately from the colored ink is attached to the recording medium prior to the ejection of the recording (colored) ink. For example, 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 reaction with a pigment, a resin emulsion, and a polyvalent metal salt. The occurrence of bleeding can be suppressed to some extent by impregnating the recording medium with the reaction liquid described therein and then reacting with the colored ink. However, when the colored ink has a high permeability to the recording medium, there is a concern about the deterioration of the color developability of the image and the problem of the see-through. On the contrary, the colored ink has a low permeability. In such a case, there is a concern that it takes time to fix the ink.

  Furthermore, as a result of intensive studies by the present inventors, in the case of a pigment ink having a configuration in which a resin is used as a pigment dispersant, a good reaction with the reaction liquid can be achieved by increasing the hydrophobicity of the resin as the dispersant. It was found that sex was obtained. However, in this case, there is another problem that the ink discharge performance is deteriorated.

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

  Accordingly, an object of the present invention is to be used for ink jet recording, exhibit high dispersion stability, good ejection, and high recording density and high bleeding suppression even when recording on plain paper. An object of the present invention is to provide a pigment ink from which a quality image can be obtained. Another object of the present invention is to provide a pigment ink production method capable of easily obtaining a pigment ink having the above-mentioned excellent characteristics, and an ink jet recording method using the pigment ink having the above-mentioned excellent characteristics. There is.

  The above object is achieved by the present invention described below. That is, the present invention includes an aqueous medium, a pigment, and two or more types of block copolymers having a hydrophobic segment and a hydrophilic segment in the structure thereof, and each block copolymer has a hydrophobic property. The pigment ink is characterized in that the structures of the sex segments are different from each other.

  The present invention also provides a method for producing a pigment ink comprising an aqueous medium, a pigment, and two or more types of block copolymers each having a hydrophobic segment and a hydrophilic segment in the structure thereof. A dispersion step in which a pigment is dispersed in an aqueous medium using any of the polymers, and a block copolymer having a hydrophobic segment structure different from that of the block copolymer used in the dispersion step in the pigment dispersion obtained in the step. And a post-addition step of adding a polymer.

  The present invention also provides a method for producing a pigment ink comprising an aqueous medium, a pigment, and two or more types of block copolymers each having a hydrophobic segment and a hydrophilic segment in the structure thereof. A method for producing a pigment ink, comprising: a dispersion step of dispersing a pigment in an aqueous medium with a mixture of two or more kinds of polymers.

  The present invention also provides a method for producing a pigment ink comprising an aqueous medium, a pigment, and two or more types of block copolymers each having a hydrophobic segment and a hydrophilic segment in the structure thereof. Dispersing step of dispersing two or more types of pigment dispersions by dispersing pigments in an aqueous medium using different block copolymers of the polymer, and mixing step of mixing two or more types of pigment dispersions obtained in the step And a method for producing a pigment ink.

  Further, the present invention uses a reaction liquid containing a substance that aggregates or gels the pigment ink by contact with the pigment ink, and applies the reaction liquid and the pigment ink to the recording medium so that they are in contact with each other. Then, in the ink jet recording method for forming an image, the pigment ink having the above-described configuration is used.

  According to the present invention, a pigment exhibiting good ink ejection characteristics, and at the same time, a pigment having excellent ink characteristics capable of giving a high-quality image with high recording density and sufficiently reduced bleeding in the boundary region between different colors. Ink is provided. Moreover, according to this invention, the manufacturing method of the pigment ink which exhibits the outstanding effect mentioned above, and the image forming method using the same can be provided.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments.
As a result of intensive studies to solve the problems of the prior art, the inventors have included two or more types of block copolymers having a structure having a hydrophobic segment and a hydrophilic segment in the pigment ink, and It has been found that a block copolymer having a specific relationship is effective. That is, as the two or more types of block copolymers to be contained in the pigment ink, block copolymers having different hydrophobic segment structures are used. And, by using the pigment ink having such a configuration, it is possible to maintain good ink jet ejection characteristics, and when image formation is performed together with the reaction liquid, the reactivity with the reaction liquid is good, the recording density is high, It was found that a high-quality image with suppressed bleeding was obtained. Hereinafter, the background that the present inventors have found that the above-described excellent effect can be obtained by the pigment ink of the present invention having the above-described configuration (hereinafter sometimes simply referred to as “ink”) will be described.

  As a result of intensive studies on a pigment ink comprising a block copolymer having a hydrophobic segment and a hydrophilic segment in its structure, the present inventors have obtained a structure depending on the structure of the hydrophobic segment of the block copolymer to be used. It was found that there is a difference in the properties obtained. Hereinafter, the “block copolymer” may be referred to as “resin”. That is, a pigment ink using a block copolymer having a high hydrophobicity in a hydrophobic segment has a good adsorptivity of the resin to the pigment and tends to have a high reactivity with the reaction solution used together with image formation. I found out. On the other hand, a pigment ink using a block copolymer having a low hydrophobicity in the hydrophobic segment is inferior in the resin adsorption to the pigment and the reactivity with the reaction liquid, but the discharge characteristics tend to be relatively good. all right.

  Although the reason is not clear, it has been found that if the resin not adsorbed on the pigment surface is present in the pigment ink, the ejection characteristics are good. That is, this suggests that when a resin having a weak adsorptivity with respect to the pigment is used, the amount of the resin not adsorbed on the pigment surface increases in the pigment ink, and the ejection characteristics are improved. Based on the knowledge obtained by the above examination, the present inventors decided to coexist two or more types of block copolymers (resins) having different hydrophobic segment structures in the composition of the pigment ink. As a result, it has been found that both the reactivity with the reaction solution used together with image formation and the ink ejection characteristics can be achieved, and a good ink jet recording image can be obtained stably. From the above examination results, in the pigment ink of the present invention comprising two or more kinds of resins, the resin having a relatively high adsorptivity with the pigment contributes to the improvement of the reactivity with the reaction liquid, and the ejection characteristics. It is considered that the resin having a relatively low adsorptivity with the pigment contributes to the improvement of the above. Hereinafter, the components of the pigment ink of the present invention will be described in detail.

<Block copolymer>
The block copolymer used in the pigment ink according to the present invention is a copolymer in which polymer segments having different repeating unit structures are bonded by a covalent bond, and is also called a block copolymer or a block polymer. Any of the two or more block copolymers constituting the pigment ink of the present invention has a hydrophobic segment and a hydrophilic segment in its structure. Specific examples of the block copolymer having such a structure include the following. For example, acrylic, methacrylic block copolymers, polystyrene and other addition polymerization or condensation polymerization block copolymers, block copolymers having polyoxyethylene and polyoxyalkylene blocks, and the like can be used. A conventionally known block copolymer can also be used. In addition, the block copolymer used in the present invention may have a structure in which a graft copolymer is formed by bonding to a certain copolymer chain in a T shape.

  In the present invention, it is preferable that at least one of the two or more types of block copolymers has a nonionic hydrophilic segment and an ionic hydrophilic segment in the structure thereof. In this case, it is particularly preferable to use an ABC triblock polymer having a structure in which a hydrophobic segment (A segment), a nonionic hydrophilic segment (B segment), and an ionic hydrophilic segment (C segment) are arranged in this order. Moreover, in this invention, it is preferable that at least any one of 2 or more types of block copolymers has a polyvinyl ether structure as a repeating unit in the structure. In this case, a vinyl ether derivative having a nonionic hydrophilic group as a functional group is preferably used as the monomer component of the block copolymer from the viewpoint of storage stability and ejection stability of the ink used for ink jet recording.

（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から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又は２を表す。Ｘ₂は、Ｘのうちｒが２の基を表す。ｐは１から１８までのいずれかの整数を表す。ｍは０から３５までのいずれかの整数を表す。ｎは１又は０を表す。ｑは０から１７のいずれかの整数を表す。Ｍは一価のカチオンを表す。Ｍ₂は二価のカチオンを表す。Ｒ₅及びＲ₆はアルキル基を表す。Ｒ₅及びＲ₆は同じでも又は異なっていてもよい。） Hereinafter, each segment that is preferably used in the block copolymer used in the present invention will be described in detail. Specific examples of the structure of the ionic hydrophilic segment include a repeating unit represented by the following general formula (1).

(In the general formula (1), R ₀ represents —X— (COOH) _r , —X— (COO—M) _r or —X ₂ — (COO) ₂ —M ₂ , where X is 1 carbon atom. To a linear, branched or cyclic alkanediyl or alkanetriyl group from 1 to 20, 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 their methylene group Represents 1 or 2. X ₂ represents a group in which r is 2 in X. p represents any integer from 1 to 18. m represents any integer from 0 to 35. Table of .R ₅ and R ₆ are alkyl groups .M representing an integer representing the cation of .M ₂ is bivalent represents a monovalent cation of n is from 0 .q is representative of a 1 or 0 17 .R ₅ and R ₆ may be the same or different.)

（一般式（２）中、Ｒ₁は、炭素数１から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から選ばれる基を表す。また、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から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。ｐは１から１８のいずれかの整数、ｍは１から３６のいずれかの整数、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から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、−ＣＨＯ、−ＣＨ₂ＣＨＯ、−ＣＯ−ＣＨ＝ＣＨ₂及び−ＣＯ−Ｃ(ＣＨ₃)＝ＣＨ₂から選ばれる基を表す。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から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、Ｐｙｒはピリジル基、Ｎｐはナフチル基を表す。） Moreover, as a specific structure of a hydrophobic segment or a nonionic hydrophilic segment, the repeating unit represented by following General formula (2) is mentioned.

(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, Represents a group selected from — (CH (R ₅ ) —CH (R ₆ ) —O) _p —R ₇ and — (CH ₂ ) _m — (O) _n —R ₇ , and a carbon atom in the aromatic ring The hydrogen atom bonded to is a linear or branched alkyl group having 1 to 4 carbon atoms, and the carbon atom in the aromatic ring may be substituted with a nitrogen atom. 18 integer of either m is an integer from 1 36, n are each the .R ₅ and R ₆ represent 0 or 1 independently represents a hydrogen atom or represents a -CH ₃ .R ₅ and R _When there are a plurality of ₆ , they may be the same or different, and R ₇ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms. A group selected from the group consisting of: -Ph, -Pyr, -Ph-Ph, -Ph-Pyr, -CHO, -CH ₂ CHO, -CO-CH = CH ₂ and -CO-C (CH ₃ ) = 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 a carbon atom in the aromatic ring can be substituted with a nitrogen atom, Ph represents a phenyl group, Pyr represents a pyridyl group, and Np represents a naphthyl group.

A number of methods for synthesizing polymers having a polyvinyl ether structure have been reported (for example, see JP-A-11-080221). Among them, the method by cation living polymerization by Aoshima et al. (See Japanese Patent Application Laid-Open Nos. 11-322942 and 11-322866) is representative. By conducting polymer synthesis by cation living polymerization, various polymers such as homopolymers, copolymers composed of two or more monomers, and block polymers, graft polymers, and gradient polymers can be used with different lengths (molecular weights). It can be synthesized with exact alignment. Moreover, various functional groups can be introduced into the side chain of the polyvinyl ether structure. In addition, the cationic polymerization method can also be carried out in a HI / I ₂ system, a HCl / SnCl ₄ system, or the like.

  The content of the block copolymer contained in the pigment ink of the present invention is not particularly limited. Usually, it is contained in the range of 0.1% by mass to 30% by mass with respect to the total mass of the ink, but more preferably in the range of 0.5% by mass to 20% by mass.

  Moreover, it is preferable that the block copolymer in this invention is an amphiphilic block copolymer. In the present invention, the amphipathic property is a property that has the property of being dissolved in two types of solvents that are not soluble together, a property that is soluble in a certain solvent and a property that is insoluble in a certain solvent, or a site that is compatible with a certain solvent. It has the property of having a site that is not compatible with the In the present invention, a copolymer composed of a hydrophilic polymer chain part (B block, C block) and a hydrophobic polymer chain part (A block) is preferable.

<Pigment>
As the pigment constituting the pigment ink of the present invention, any conventionally known inorganic pigment and organic pigment can be used. Carbon black is suitable as the pigment used in the black ink. Examples of the carbon black pigment include furnace black, lamp black, acetylene black, and channel black. Among these, carbon black pigments having the following characteristics are particularly preferable. The DBP oil absorption is 40 ml / 100 g or more and 200 ml / 100 g or less, the primary particle diameter is 15 mμ (nm) or more and 40 mμ (nm) or less, the BET method specific surface area is 50 m ² / g or more and 400 m ² / g or less, and the volatile content is 0.00. 5% or more and 10% or less, and the pH value is 2 to 9.

  Examples of the carbon black having such characteristics include the following commercially available products. Raven 7000, 5750, 5250, 5000 ULTRA, 3500, 2000, 1500, 1250, 1200, 1190 ULTRA-II, 1170, 1255 (above Colombia). Black Pearls L, Regal 400R, 330R, 660R, Mogul L (above Cabot). Monarch 700, 800, 880, 900, 1000. Same 1100, Same 1300, Same 1400, Vulcan XC-72R (manufactured by Cabot). Color Black (Color Black) FW1, FW2, FW2V, FW18, FW200, S150, S160, S170 (above Degussa). Printex 35, U, V, Printex 140U, 140V, Special Black 6, 5, 4A, 4 (more from Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical). In addition, a newly prepared one can be used.

  Specific examples of the organic pigment constituting the pigment ink of the present invention include the following. Insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, and Pyrazolone Red. 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. Thioindigo pigment. Condensed azo pigment. Thioindigo pigment. Diketopyrrolopyrrole pigment. Other pigments such as flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet can be exemplified.

Moreover, when an organic pigment is shown by a color index (CI) number, the following can be used.
C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148. 150, 151, 153, 154, 166, 168, 180, 185.
C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71.
C. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192. 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272.
C. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50.
C. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 22 and 60, 64.
C. I. Pigment Green 7 and 36.
C. I. Examples thereof include CI Pigment Brown 23, 25, and 26.

  Among these pigments, those listed below are more preferable. That is, C.I. I. Pigment Yellow 74, 93, 97, 110, 120, 128, 138, 147, 148, 150, 151, 154, 155, 180, and 185. C. I. Pigment red 122, C.I. I. Pigment violet 19, C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, and the like are more preferable.

  Here, the content of the pigment as described above in the ink is, for example, such that when the ink is used for ink jet recording, the ink has excellent ink jet discharge characteristics and has a desired color tone and density. What is necessary is just to select suitably. As a guide, a range of 0.1% by mass to 20% by mass with respect to the total mass of the ink is preferable, and a range of 0.5% by mass to 10% by mass is more preferable.

  The particle diameter (average particle diameter) of the pigment constituting the ink of the present invention is not particularly limited, but is preferably 0.5 μm or less, more preferably 100 nm or less. By using a pigment having a particle diameter (average particle diameter) of 0.5 μm or less, the occurrence of clogging at the discharge port can be suppressed, and further sufficient ink discharge stability can be realized. As a method for making the pigment into fine particles, for example, the following methods can be used. A method of applying strong grinding with a bead mill, a mechanical method using a jet mill, etc., a method of making the primary particle diameter as fine as possible and a pigment with low surface activity at the time of pigment synthesis, in an inert gas There is a method such as atomization by an evaporation method, that is, a gas phase method. Moreover, the measurement of the average particle diameter of a pigment can be calculated | required with the commercially available particle size measuring apparatus using a light-scattering method, an electrophoresis method, a laser Doppler method, etc.

<Aqueous medium>
The aqueous medium constituting the ink of the present invention is preferably a mixed solvent (aqueous medium) of water and a water-soluble organic solvent. As the water-soluble organic solvent used in this case, those having an ink drying preventing effect are particularly preferable. Moreover, it is preferable to use deionized water instead of general water containing various ions.

  Specific examples of the water-soluble organic solvent used in the present invention include the following. C1-C5 alkyl alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pentanol. Amides such as dimethylformamide and dimethylacetamide. Ketones or ketoalcohols such as acetone and diacetone alcohol. Ethers such as tetrahydrofuran and dioxane. Oxyethylene or oxypropylene copolymers such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol. Alkylene glycols in which an alkylene group contains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, trimethylene glycol, triethylene glycol and 1,2,6-hexanetriol; Glycerin. Lower alkyl ethers such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether. Lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether. Alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine. Examples include sulfolane, N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. The water-soluble organic solvents mentioned above can be used alone or as a mixture.

  The content of the water-soluble organic solvent as described above contained in the ink of the present invention is not particularly limited, but is preferably in the range of 3% by mass to 50% by mass with respect to the total mass of the ink. The content of water contained in the ink is preferably in the range of 50% by mass to 95% by mass with respect to the total mass of the ink.

<Other ingredients>
In addition to the above-described components, the ink of the present invention may be added as necessary, for example, various surfactants, ultraviolet absorbers, stabilizers, viscosity, in order to obtain inks having desired physical properties. An adjuster, an antifoaming agent, an antiseptic, an antifungal agent, an antioxidant and the like can be added.

  Although it does not specifically limit as an additive, Specifically, the following can be used. Polyoxyethylene alkylphenyl ether sulfates such as polyoxyethylene nonylphenyl ether sulfate. Polyoxyethylene alkyl ether phosphates such as polyoxyethylene dodecyl ether phosphates. C12-22 polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether. Polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether. Polyoxyethylene adducts of acetylene diol. Polyoxyethylene-polyoxypropylene block polymer and alkyl ethers thereof. Polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters. Polyoxyethylene sorbitol fatty acid esters. And polyethylene glycol fatty acid esters such as polyethylene glycol lauryl ester. These may be used alone or in appropriate combination of two or more. The additive is preferably selected so that the surface tension of the ink is 25 mN / m or more, preferably 28 mN / m or more.

  The above is the description of each component constituting the pigment ink of the present invention. The average particle diameter of the pigment in the pigment ink of the present invention is preferably in the range of 50 nm to 200 nm. Examples of the method for measuring the average particle diameter of pigment in the pigment ink include ELS-8000 (manufactured by Otsuka Electronics), Microtrac UPA150 (manufactured by Nikkiso) and the like using laser light scattering.

<Method for producing pigment ink>
As a method for producing the pigment ink of the present invention comprising two or more types of block copolymers having an aqueous medium, a pigment, and a hydrophobic segment and a hydrophilic segment in the structure, the following three types of methods can be used. Can be mentioned.

  The first method is a dispersion step in which a pigment is dispersed in an aqueous medium using any one of block copolymers, and the block copolymer used in the dispersion step in the pigment dispersion obtained in the step is a hydrophobic segment. And a post-addition step of adding block copolymers having different structures. By this production method, the pigment ink of the present invention, in which the pigment is dispersed in one of two or more block copolymers and is not dispersed in any other block copolymer, is obtained. Can do.

  The second method is characterized by having a dispersion step of dispersing the pigment in an aqueous medium with a mixture obtained by mixing two or more kinds of the block copolymers. By this production method, it is possible to obtain the pigment ink of the present invention, in which the pigment is dispersed by two or more kinds of block copolymers.

  A third method includes a dispersion step of dispersing two or more types of pigment dispersions by dispersing pigments in an aqueous medium using different block copolymers of the block copolymers, and two or more types of the block copolymers obtained in the step. And a mixing step of mixing the pigment dispersion. By this production method, the pigment ink of the present invention is a pigment in which the pigment is dispersed in one of two or more types of block copolymers and a pigment in which the pigment is dispersed in other block copolymers. A pigment ink can be obtained. Hereinafter, these methods will be described.

  In the first method, the ink of the present invention is obtained as follows. First, two or more types of block copolymers having a hydrophobic segment and a hydrophilic segment in the structure and having different hydrophobic segments are prepared. A predetermined amount of pigment is added to a solution containing a predetermined amount of any of the prepared block copolymers, and after sufficient stirring, a dispersion process is performed using a disperser. Thereafter, coarse particles are removed from the pigment dispersion solution with a centrifuge. Thereafter, an aqueous solution of the block copolymer other than that used above, a predetermined aqueous medium, and other additives as necessary are added to the pigment dispersion thus obtained. Subsequently, the ink of the present invention is obtained by stirring and mixing and filtering.

  Also in the second method, first, two or more block copolymers having a hydrophobic segment and a hydrophilic segment in the structure and having different hydrophobic segments are prepared. In the second method, a predetermined amount of pigment is added to a predetermined amount of solution containing both of the two or more types of prepared block copolymers, and after sufficient stirring, dispersed using a disperser. Process. Thereafter, coarse particles are removed from the dispersion solution of the pigment by centrifugation or the like, and then a predetermined aqueous medium and, if necessary, other additives are added. Subsequently, the ink of the present invention is obtained by stirring and mixing and filtering.

  Also in the third method, first, two or more block copolymers having a hydrophobic segment and a hydrophilic segment in the structure and having different hydrophobic segments are prepared. In the third method, each pigment dispersion is obtained by separately using two or more types of prepared block copolymers. That is, each pigment dispersion uses a different block copolymer, a predetermined amount of pigment is added to each solution containing a predetermined amount of each block copolymer, and after sufficient stirring, a dispersion treatment is performed using a disperser. It is obtained by doing. Then, the pigment dispersions thus obtained are mixed at a predetermined mixing ratio, a predetermined aqueous medium, and other additives as necessary are added, followed by stirring and mixing, and filtration. By performing this, the ink of the present invention is obtained.

  Moreover, when manufacturing the pigment ink of this invention, the method of producing a pigment dispersion liquid with high pigment concentration, and diluting at the time of ink preparation can also be used. Any commercially available disperser may be used, and examples include the following. Colloid mill, flow jet mill, slasher mill, high speed disperser, ball mill, attritor, sand mill, sand grinder, ultra fine mill, Eiger motor mill, dyno mill, pearl mill, agitator mill, cobol mill. Examples include an extruder, a kneader, a microfluidizer, a laboratory homogenizer, an ultrasonic homogenizer, a nanomizer, a roll mill, an agitator, a Henschel mixer, a wet jet mill, and a paint shaker. These may be used alone or in combination. Alternatively, after mixing a predetermined solvent, water, and a dispersant, a pigment may be added and dispersed using a disperser.

<Inkjet recording method>
Next, the ink jet recording method of the present invention will be described. The ink jet recording method of the present invention uses a reaction liquid containing a substance that aggregates or gels the pigment ink by contact with the pigment ink, and the recording medium is in contact with the reaction liquid and the pigment ink. To form an image. At that time, the pigment ink of the present invention described above is used. Further, in the ink jet recording method of the present invention, a reaction liquid having an acid basicity opposite to that of the pigment ink of the present invention is used, and the ink and the reaction liquid are in contact with each other on a recording medium. It is preferable that

In the ink jet recording method of the present invention, as the reaction liquid, a conventionally known one containing a substance that aggregates or gels the pigment ink by contact with the pigment ink can be used. Specific examples of the substance (reactant) that aggregates or gels the pigment ink contained in the reaction liquid include polyvalent metal salts. The polyvalent metal salt is composed of a divalent or higher polyvalent metal ion and an anion that binds to these polyvalent metal ions. Examples of the polyvalent metal ions include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , and Zn ^2+, and trivalent metal ions such as Fe ³⁺ and Al ^3+. It is done. Examples of the anion include Cl ⁻ , NO ₃ ⁻ , SO ₄ ^{2− and the} like. The content of the reactant is not particularly limited, but is preferably in the range of 0.01 to 30% by mass based on the total mass of the reaction solution. Examples of the aqueous medium contained in the reaction liquid include water or a mixed solvent of water and a water-soluble organic solvent. As the water-soluble organic solvent, for example, those mentioned in the description of the ink can be used. The content of water is preferably in the range of 50 to 95% by mass based on the total mass of the reaction solution, and the content of the water-soluble organic solvent is 5 to 60% by mass based on the total mass of the reaction solution. A range is preferable. Moreover, you may mix | blend additives, such as a viscosity adjuster, a pH adjuster, and antioxidant, with a reaction liquid suitably as needed.

  The ink jet recording method of the present invention is not limited as long as the pigment ink of the present invention applied by the ink jet recording method and the reaction liquid having the configuration as described above are brought into contact with each other when applied to a recording medium. This method may be used. In the inkjet recording method of the present invention, it does not matter which of the pigment ink and the reaction liquid is applied to the recording medium first. Further, when the reaction liquid is first adhered to the recording medium, the time from when the reaction liquid is adhered to the recording medium until the pigment ink is adhered onto the recording medium is not particularly limited. For example, a method of attaching the pigment ink and the reaction liquid almost simultaneously, or a method of attaching the pigment ink to the recording medium to which the reaction liquid is attached within several seconds after the reaction liquid is attached to the recording medium can be preferably used. . The recording medium used in the above-described image forming method is not particularly limited, and so-called plain paper such as copy paper and bond paper that has been conventionally used is preferably used. Of course, a coated paper specially prepared for inkjet recording and a transparent film for OHP can also be suitably used. Furthermore, general high quality paper and glossy paper can also be suitably used.

  In the inkjet recording method of the present invention, the method for applying the reaction liquid is not particularly limited. The method for attaching the reaction liquid onto the recording medium is not particularly limited. For example, a method of adhering to the entire surface of the recording medium with a spray or a roller can be mentioned. Preferably, it is carried out by an ink jet recording method in which the reaction liquid can be selectively and uniformly attached only to the region where the pigment ink adheres, or only to the region and the vicinity of the region. In this case, various ink jet recording methods can be used, but a method of discharging droplets using bubbles generated by thermal energy is particularly preferable. Here, the region to which the pigment ink adheres refers to a region to which the pigment ink dots adhere, and the vicinity of the region refers to 1 to 5 outside the region to which the pigment ink dots adhere. An area that is about a dot apart.

  The ink jet recording method used in the present invention may be any method. For example, there are a recording method for ejecting ink by applying mechanical energy to the ink, and an ink jet recording method for ejecting ink by foaming of the ink by applying thermal energy to the ink. These ink jet recording methods are particularly suitable as a method for applying the pigment ink of the present invention to a recording medium.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the text, “part” is based on mass unless otherwise specified.

<Synthesis of block copolymer>
(Synthesis of block copolymer P1)
First, the block copolymer P1 was synthesized by the following procedure. ABC triblock using 4-methylphenylethyl vinyl ether as the raw material for the A block, 2- (2-methoxyethyl) ethyl vinyl ether as the raw material for the B block, and ethyl 4- (2-vinyloxy) ethoxybenzoate as the raw material for the C block A polymer was synthesized. The obtained ABC triblock polymer was designated as block copolymer P1. In this example, the block copolymer was identified by using NMR (nuclear magnetic resonance spectroscopy) and GPC (Gel Permeation Chromatography). The obtained block copolymer P1 has a number average molecular weight of 20,100 and Mw / Mn (weight average molecular weight / number average molecular weight) = 1.17, and the degree of polymerization of each block is A, B, C, They were 89, 40, and 14, respectively.

(Synthesis of block copolymer P2)
A block copolymer P2, which is an ABC triblock polymer, was synthesized by the same method as the synthesis of the block copolymer P1, except that phenylethyl vinyl ether was used as a raw material for the A block. The resulting block copolymer P2 had a number average molecular weight of 18,400 and Mw / Mn = 1.19, and the degree of polymerization of each block was A, B, C, 90, 40, 13 respectively. .

(Synthesis of block copolymer P3)
A block copolymer P3, which is an ABC triblock polymer, was synthesized by the same method as the synthesis of the block copolymer P1, except that naphthalene vinyl ether was used as a raw material for the A block. The resulting block copolymer P3 had a number average molecular weight of 10,700 and Mw / Mn = 1.18, and the degree of polymerization of each block was A, B and C, 48, 10 and 9, respectively. .

(Synthesis of block copolymer P4)
A block copolymer P4, which is an ABC triblock polymer, was synthesized by the same method as the synthesis of the block copolymer P1 except that the amount of the A block raw material was changed. The obtained block copolymer P4 had a number average molecular weight of 14,100 and Mw / Mn = 1.16, and the degree of polymerization of each block was 59, 21, and 8 for A, B, and C, respectively. .

(Synthesis of block copolymer P5)
An AB diblock polymer was synthesized by using naphthalene vinyl ether as a raw material for the A block and ethyl 4- (2-vinyloxy) ethoxybenzoate as a raw material for the B block, to obtain a block copolymer P5. The resulting block copolymer P5 had a number average molecular weight of 14,400 and Mw / Mn = 1.08, and the degree of polymerization of each block was 71 and 17, respectively.

(Synthesis of block copolymer P6)
A block copolymer P6, which is an AB diblock polymer, was synthesized by the same method as the synthesis of the block copolymer P5 except that 4-methylphenylethyl vinyl ether was used as a raw material for the A block. The obtained block copolymer P6 had a number average molecular weight of 17,600 and Mw / Mn = 1.09, and the degree of polymerization of each block was 89 and 13, respectively.

<Preparation of pigment dispersion or aqueous resin solution>
(Preparation of pigment dispersions D1 to D12)
Pigment dispersions D1 to D12 were prepared by the following procedure. Place a flask equipped with a mechanical stirrer in the tank of the ultrasonic generator, add tetrahydrofuran, the specified amount of the block copolymer obtained above and 20.0 g of carbon black, and stir well. did. Thereafter, an alkaline aqueous solution containing KOH (potassium hydroxide) with which the neutralization rate of the block copolymer was 100% was dropped. Next, using a sand grinder manufactured by Igarashi Machine, dispersion treatment was performed for 3 hours using zirconia beads having a diameter of 1 mm. Thereafter, tetrahydrofuran was distilled off using a rotary evaporator to obtain a pigment dispersion. Table 1 shows the types and amounts of the block copolymers used in the obtained pigment dispersions D1 to D12.

(Preparation of aqueous resin solution PS1)
A flask equipped with a mechanical stirrer is placed in a tank of an ultrasonic generator, in which 10 g of block copolymer P2 and KOH with a neutralization rate of 100% are obtained. An aqueous alkali solution containing was added and stirred well to prepare an aqueous resin solution PS1.

(Preparation of aqueous resin solution PS2)
A resin aqueous solution PS2 was produced in the same manner as the resin aqueous solution PS1, except that the block copolymer P2 used for the production of the resin aqueous solution PS1 was replaced with the block copolymer P4.

(Preparation of aqueous resin solution PS3)
A resin aqueous solution PS3 was produced in the same manner as the resin aqueous solution PS1, except that the block copolymer P2 used for the production of the resin aqueous solution PS1 was replaced with the block copolymer P6.

<Preparation of pigment ink>
(Preparation of pigment inks K1 to K15)
As shown in Table 2, the pigment dispersion and resin aqueous solution prepared above were used alone or in combination, and a water-soluble organic solvent, an additive, and ion-exchanged water were added thereto so as to have the following composition. Then, it filtered using a 1 micrometer filter and adjusted pigment ink K1-K15. In addition, about the pigment ink which combined two types of pigment dispersion liquids, and the pigment ink which combined the pigment dispersion liquid and resin aqueous solution, the ratio of two types of block copolymers in the completed pigment ink is 1: 1. It mix | blended so that it might become. Table 2 also shows the types of block copolymers used in the pigment inks K1 to K15.

(Composition of pigment ink)
-Carbon black 3.5 parts-Block copolymer (total) 3.5 parts-Glycerol 7 parts-Diethylene glycol 7 parts-Trimethylolpropane 7 parts-Acetylene glycol surfactant 0.5 parts-Nonionic surfactant 0. 5 parts, 71 parts of ion exchange water

<Preparation of reaction solution>
A solvent and an additive were added to ion-exchanged water in the following composition, and after sufficiently stirring, pressure filtration was performed with a microfilter having a pore size of 0.2 μm to prepare a reaction solution.

(Composition of reaction solution)
・ Diethylene glycol 10.0 parts ・ Methyl alcohol 5.0 parts ・ Magnesium nitrate 3.0 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 0.1 part ・ Ion-exchanged water 81.9 parts

<Evaluation>
Each ink of Examples 1 to 9 (inks K1 to K9) and Comparative Examples 1 to 6 (inks K10 to K15) was evaluated using an inkjet printer as follows. In the following series of evaluation items, the recording medium used as plain paper is PB paper manufactured by Canon Inc. The recording head used had a recording density of 1,200 dpi, and the driving condition was a driving frequency of 15 kHz. Further, a 4 pl head was used for the ejection volume per dot. The environmental conditions (temperature / relative humidity) during the printing test are unified to 25 ° C./55% RH.

[Evaluation item]
(1) Evaluation of ejection characteristics Inks K1 to K15 were respectively mounted on an ink jet printer BJ-F930 (manufactured by Canon Inc.), and 10 million alphanumeric characters were continuously printed in two passes. Each printed matter was visually observed to confirm the printed state. The evaluation criteria are as follows. The evaluation results are shown in Table 3.
A: There was almost no blurring of printing, no ejection, etc., and printing could be completed to the end.
○: Some printing blur occurred.
X: Problems such as printing blur and non-ejection have occurred.

(2) Bleeding evaluation Ink jet printer BJ-F930 (manufactured by Canon Inc.), inks K1 to K15 prepared above, reaction solution prepared above, and yellow ink for printer (BCI-6Y: Canon) (Made by Co., Ltd.). Next, each of the inks K1 to K15 prepared above and a solid image of yellow ink were printed in two passes adjacent to each other, and the degree of bleeding at the boundary portion of each color was visually observed. The evaluation focuses on the color boundary where the bleed is most generated in the adjacent portions of each color, and the determination criteria are as follows. The evaluation results are shown in Table 3.
A: Bleeding hardly occurs.
○: Some bleeding occurred.
X: Bleeding has occurred.

(3) Evaluation of optical density The optical density of the solid print area of the ink was measured with a reflection densitometer RD-19I (manufactured by GretagMacbeth) using each image produced by the above evaluation of bleeding. The evaluation criteria are as follows. The evaluation results are shown in Table 3.
○: Reflection density is 1.4 or more.
X: Reflection density is less than 1.4.

  According to the present invention, it is possible to obtain a pigment ink that has both good ejection characteristics and ink characteristics that can provide a high-quality image with high recording density and sufficiently reduced bleeding in the boundary region between different colors. Further improvement of the ink jet recording technology can be expected.

Claims (10)

  The aqueous medium, the pigment, and the structure thereof include two or more types of block copolymers having a hydrophobic segment and a hydrophilic segment, and the structures of the hydrophobic segments of the respective block copolymers are mutually Pigment ink characterized by being different.   The pigment ink according to claim 1, wherein the pigment is dispersed in any one of the two or more types of block copolymers and is not dispersed in any other block copolymer.   The pigment ink according to claim 1, wherein the pigment is dispersed by two or more types of the block copolymer.   The pigment ink according to claim 1, wherein the pigment is a pigment dispersed in any one of the two or more types of block copolymers and a pigment dispersed in other block copolymers.   The pigment ink according to any one of claims 1 to 4, wherein at least one of the two or more types of block copolymers has a nonionic hydrophilic segment and an ionic hydrophilic segment in the structure thereof.   The pigment ink according to any one of claims 1 to 5, wherein at least one of the two or more types of block copolymers has a polyvinyl ether structure as a repeating unit in the structure thereof.   A method for producing a pigment ink comprising an aqueous medium, a pigment, and two or more types of block copolymers each having a hydrophobic segment and a hydrophilic segment in the structure thereof, wherein any one of the block copolymers described above is used. Using a dispersion step of dispersing a pigment in an aqueous medium, and after adding a block copolymer having a hydrophobic segment structure different from that of the block copolymer used in the dispersion step to the pigment dispersion obtained in the step And a step of adding the pigment ink.   A method for producing a pigment ink comprising an aqueous medium, a pigment, and a block copolymer having two or more types of block copolymers each having a hydrophobic segment and a hydrophilic segment in the structure thereof, wherein the two or more types of the block copolymer are used. A method for producing a pigment ink, comprising a dispersion step of dispersing a pigment in an aqueous medium using a mixed mixture.   A method for producing a pigment ink comprising an aqueous medium, a pigment, and a block copolymer having two or more types of block copolymers each having a hydrophobic segment and a hydrophilic segment in its structure. A dispersion step of dispersing two or more types of pigment dispersions by dispersing a pigment in an aqueous medium with a block copolymer, and a mixing step of mixing two or more types of pigment dispersions obtained in the step A method for producing a pigment ink.   Using a reaction liquid containing a substance that aggregates or gels the pigment ink by contact with the pigment ink, the reaction liquid and the pigment ink are applied to a recording medium so as to be in contact with each other to form an image. 7. An ink jet recording method comprising using the pigment ink according to claim 1 in the ink jet recording method.