JP2009298842A - Ink set for inkjet recording and method for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set capable of high-speed printing even when printed on plain paper for inkjet recording and producing an image with high record concentration, high scratch resistance and high marker resistance; and to provide a method for recording using the ink set. <P>SOLUTION: An ink set for inkjet recording comprises independently a recording solution containing at least a dispersed resin and carbon black as well as a reaction solution containing a reactive substance having reactivity with the dispersed resin. In the ink set, the amount of the dispersed resin adsorbed per gram of the carbon black A (g/g) and the amount of DBP oil absorption per gram of the carbon black B (g/g) satisfy the following relation: 0.2≤A/B≤0.6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink set for ink-jet recording and an ink-jet recording independently comprising a recording liquid containing at least a carbon block and a reaction liquid having reactivity with the recording liquid for use in an image recording apparatus of an ink-jet recording system. Regarding the method. More specifically, an ink set for ink-jet recording, which is capable of high-speed printing, particularly on plain paper, has excellent scratch resistance and marker resistance, and provides a recorded matter with a high recording density, and the ink set. The present invention relates to an ink jet recording method using.

  In the ink jet recording method, recording is performed by causing a small droplet of a recording liquid (hereinafter, “recording liquid” may be referred to as “ink”) to fly and adhere to a recording medium such as paper. In particular, according to an ink jet recording method (for example, see Patent Documents 1 to 3), an electrothermal transducer is used as the ejection energy supply means, and droplets are ejected by applying thermal energy to the ink to generate bubbles. Excellent effects can be obtained. That is, a high-density multi-orifice of the recording head can be easily realized, and high-resolution and high-quality images can be recorded at high speed.

  However, the ink used in the conventional ink jet recording method generally contains water as a main component and contains a 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 ink, the ink penetrates into the inside of the recording paper, and a sufficient recording density cannot be obtained, or there is no filler or sizing agent on the surface of the recording paper. The image density may be non-uniform, which may be due to the uniform distribution.

  For these issues, the particle diameter, DBP oil absorption, pH, and the relationship of the carbon black to be used are specified with the aim of improving the recording density of printed matter on plain paper with colored ink using carbon black as the colorant. Ink has been proposed (see, for example, Patent Document 4). However, when printing on plain paper with colored ink using carbon black having such characteristics, the permeability to the recording paper is reduced, and if it is not an ink with a slow drying speed, a recorded matter having a sufficient recording density will be obtained. Couldn't get. That is, even if the ink as shown in the above proposal is used, it is impossible to achieve both high-speed printing and recording density of recorded matter on plain paper.

  On the other hand, in order to solve the above-described problems, various methods have been proposed as a method for suppressing a decrease in the recording density of a recorded matter, in which a liquid that causes an image to be satisfactorily adhered to the recording paper before the recording liquid is jetted. . For example, there is a proposal of a printing method in which a solution of a polymer such as carboxymethyl cellulose, polyvinyl alcohol, or polyvinyl acetate is jetted onto a recording medium in advance (see, for example, Patent Document 5). However, in this method, although the recording density of the recorded matter is improved, there is a problem that the solution itself is poorly dried and high-speed printing cannot be performed.

  Various proposals have been made to improve this. For example, there is a proposal of a method for recording an ink containing an anionic dye after attaching a liquid containing an organic compound having two or more cationic groups per molecule to a recording medium (for example, Patent Document 6). reference). In addition, there is a proposal of a method for recording ink after an acidic liquid containing succinic acid or the like is attached to a recording medium (see, for example, Patent Document 7). In addition, there is a proposal of a method in which a liquid that insolubilizes a dye is attached to a recording medium before ink is recorded (see, for example, Patent Document 8). Furthermore, a proposal has been made to increase the recording material density by using the reaction between polyvalent metal ions and carboxyl groups to increase the color material aggregation rate (see, for example, Patent Document 9).

  However, in these cases, there is a problem that bleeding occurs when the printed material is rubbed with a finger or a marker because the color material is fixed on the surface layer of the recording medium. Furthermore, there is also a proposal of a method for improving such bleeding by utilizing a reaction of a pigment, a resin emulsion, and a polyvalent metal salt (see, for example, Patent Document 10). It is almost the same and has not yet solved the problem.

  In addition, an ink set in which a recording liquid containing a resin-coated color material and a reaction liquid containing fine particles having reactivity with the color material are combined for lack of scratch resistance of the recorded matter (for example, (See Patent Document 11). In the ink set having this configuration, the resin-coated color material is used to improve the scratch resistance and marker resistance of the recorded matter. However, when the ink set having this configuration is used, the color material is coated with a resin, so that the reactivity of the color material is lowered, and it is difficult to avoid a decrease in the recording density of the color material.

  As described above, in the proposals made so far, there is a trade-off relationship between the fixing speed, the recording density of the recorded matter, and the scratch resistance and marker resistance of the recorded matter, and an ink set that can satisfy all of them. No proposal has been made for.

Japanese Patent Publication No. 61-59911 Japanese Patent Publication No. 61-59912 Japanese Examined Patent Publication No. 61-59914 JP-A-7-316480 JP-A-56-89595 JP-A 63-299971 Japanese Unexamined Patent Publication No. 64-9279 JP-A-64-63185 JP-A-5-202328 JP-A-9-207424 JP 2003-266916 A

  Accordingly, an object of the present invention is an ink set that can perform high-speed printing even when recording on plain paper for inkjet recording, and can provide an image with high recording density, scratch resistance, and marker resistance. Is to provide. Another object of the present invention is to provide an ink jet recording method using the above ink set.

  The above object can be achieved by the following configurations of the present invention. That is, the present invention relates to the above carbon black in an ink set independently comprising a recording liquid comprising at least a dispersion resin and carbon black and a reaction liquid comprising a reactive substance having reactivity with the dispersion resin. The relationship between the adsorption amount A (g / g) adsorbed by the dispersion resin per gram and the DBP oil absorption amount B (g / g) per gram of the carbon black is 0.2 ≦ A / B ≦ 0.6. An ink set for inkjet recording, characterized in that

  Another embodiment of the present invention includes a step of applying a reaction liquid constituting the ink jet recording ink set onto a recording medium, and a recording liquid constituting the ink jet recording ink set. An inkjet recording method comprising: forming the image by bringing the reaction liquid and the recording liquid into contact with each other on a recording medium.

  According to the present invention, there is provided an ink set for ink jet recording, which is capable of high-speed printing even when recorded on plain paper, and can obtain an image having both high recording density and scratch resistance and marker resistance. be able to. In addition, according to the present invention, it is possible to provide an inkjet recording method that uses the ink set and has a high practical value for obtaining the excellent image.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. As described above, in recording on plain paper using inkjet ink, in order to improve the recording density of the recorded matter, the absorption (penetration) speed of the recording liquid into the recording medium, The relationship between the aggregation speeds of the color materials on the recording medium is important. For this reason, for example, by using ink with high surface tension and suppressing the permeation rate of the recording liquid into the recording medium, or by using a reaction liquid containing a polyvalent metal salt, the color material aggregation rate There are proposals to increase However, if the penetration speed of the recording liquid is suppressed excessively, high-speed printing tends to be difficult, and if the aggregation rate of the coloring material is increased only by the method using the reaction liquid, the scratch resistance and resistance of the recorded matter are increased. Another problem is that the marker property is low. For this problem, as described above, it has been proposed to improve the scratch resistance and marker resistance of a recorded matter by coating a color material with a resin. However, in the case of this method, the inventors have found that the resin coating of the color material reduces the aggregation speed of the color material and leads to a decrease in the recording density of the recorded matter.

  Further, according to the study by the present inventors, in the case of an ink using carbon black as a coloring material, it is possible to increase the aggregation rate of the pigment without decreasing the absorption (penetration) rate of the recording liquid into the recording medium. It is necessary to control the DBP oil absorption amount of carbon black and the adsorption amount of the dispersion resin. The present invention has been made based on these findings. Hereinafter, the necessity of controlling the DBP oil absorption amount of carbon black and the adsorption amount of the dispersion resin will be described. First, the DBP oil absorption is measured according to JIS K6217 or DIN 53 601 and means the degree of connection between primary particles of carbon black. The high DBP oil absorption is a connection between primary particles. Means big. And, according to the study by the present inventors, the amount of DBP oil absorption is large, that is, by using a bulky carbon black connected with high-order carbon black, the aggregation speed of carbon black as a coloring material is increased, The recording density of the recorded matter can be improved. The reason for this is that when carbon black having a high DBP oil absorption is used, the effective volume of carbon black in the ink is increased, and therefore the number of contacts between carbon blacks on the recording medium is increased. Conceivable. On the other hand, if carbon black having a large amount of resin adsorbed on carbon black is used as the color material, it is considered that the scratch resistance and marker resistance of the recorded matter can be improved. However, as a result of detailed investigations by the present inventors, if the amount of adsorption of the resin on the carbon black increases, the effect of increasing the aggregation speed of the carbon black obtained when carbon black having a high DBP oil absorption is used is generated. Was found to be inhibited. This indicates that the resin adsorbed on the carbon black in the ink inhibits the improvement of the cohesiveness of the carbon black. That is, in controlling the cohesiveness of carbon black, it is important to consider the relationship between the amount of resin adsorbed on carbon black, particularly the amount of adsorption of the dispersed resin. The amount of the resin adsorbed on the carbon black can be measured by using a Poiseuille flow generated by flowing a liquid through a narrow capillary diameter and using an apparatus that can separate particles having different particle diameters. An example of the apparatus is CHDF2000 (manufactured by Matec Applied Sciences).

  As a result of further detailed studies by the present inventors based on the above findings, the present invention has been achieved. In the present invention, in an ink set having independently an ink comprising at least a dispersion resin and carbon black and a reaction liquid comprising a reactive substance having reactivity with the dispersion resin, the ink has the following constitution It is characterized by using the thing. That is, the relationship between the adsorption amount A (g / g) of the dispersed resin per gram of carbon black and the oil absorption amount B (g / g) per gram of carbon black is 0.2 ≦ A / B ≦ 0.6. By using ink, the following excellent effects can be obtained. By using the ink having the above configuration in combination with the dispersion resin in the ink and the reactive reaction liquid, high-speed printing is possible on plain paper, and the recording density, scratch resistance, and marker resistance are high. Both can provide high images. The reason why such an excellent effect can be obtained is as follows. That is, in the range where A / B is 0.6 or less, carbon black is not completely coated with the dispersion resin, and in this case, carbon black probably has an exposed surface. It is considered that this exposed surface increases the aggregation speed of carbon black. On the other hand, if A / B is less than 0.2, the exposed surface of the carbon black increases too much, and in this case, it is considered that the scratch resistance and marker resistance of the recorded matter deteriorate. Furthermore, in the present invention, the configuration of the reaction liquid used in combination with the above ink contains a substance having reactivity with the dispersion resin in the ink, so that high-speed printing can be performed on plain paper. .

  The ink set for ink-jet recording of the present invention comprising the ink having the above-described configuration and the reaction liquid independently is suitably used for the ink-jet recording method of the present invention having the following configuration. That is, the inkjet recording method of the present invention includes a step of applying a reaction liquid having the above-described configuration onto a recording medium, and a step of applying an ink having the above-described configuration to a recording medium. An image is formed by bringing a liquid and the ink into contact with each other on a recording medium. Hereinafter, each of the ink and the reaction liquid constituting the ink set of the present invention will be described.

<Recording liquid (ink)>
The ink that constitutes the ink set of the present invention is used in combination with a reaction liquid described later, but any ink that contains at least a dispersion resin and carbon black may be used. Therefore, the ink set of the present invention may have a plurality of inks independently of this ink. The content of the pigment contained in these inks is preferably 0.1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 5% by mass or less, based on the total mass of the ink. By setting the pigment content to 0.1% by mass or more, a sufficient recording density can be ensured. Further, by setting the pigment content to 10% by mass or less, it is possible to ensure more sufficient ejection stability without causing structural viscosity in the ink viscosity characteristics. Further, by making the pigment content 2% by mass or more and 5% by mass or less, it is possible to improve the discharge stability of the ink and the recording density of the recorded matter.

The carbon black used in at least the ink comprising the dispersion resin and carbon black constituting the ink set of the present invention is required to satisfy the following requirements. That is, the relationship between the amount of adsorption A (g / g) of the dispersion resin per gram of carbon black and the amount of DBP oil absorption B (g / g) per gram of carbon black is 0.2 ≦ A / B ≦ 0.6. It is necessary to be. Any material may be used as long as this requirement is satisfied, but those having a DBP oil absorption B (g / g) of 1.0 g / g or more are particularly preferable. As such carbon black, for example, carbon black produced by a furnace method or a channel method can be used. Furthermore, in the present invention, the primary particle diameter is 13 nm to 40 nm, the specific surface area by the BET method is 50 m ² / g to 300 m ² / g, the volatile content is 0.5% to 10%, and the pH value is 2 to 2. Those having characteristics such as 9 are preferably used.

  Examples of commercially available products having such characteristics include Monarch 700 (manufactured by Cabot Special Chemicals), Color Black FW18, Printex L6 (manufactured by Degussa), and any of these can be preferably used. Of course, the carbon black used in the present invention is not limited to the above, and newly manufactured carbon black can also be used.

  As described above, the ink set according to the present invention uses, in addition to the ink containing carbon black, another ink using a pigment other than carbon black for colorization. Also good. Examples of yellow pigments used at this time include C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 2, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 13. C. I. Pigment Yellow 16, C.I. I. Pigment Yellow 83, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 109, C.I. I. Pigment Yellow 128 or the like. Examples of magenta pigments include C.I. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn). C. I. Pigment Red 57 (Ca), C.I. I. Pigment Red 112, C.I. I. Pigment Red 122 or the like. Examples of cyan pigments include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15: 4. C. I. Pigment Blue 16, C.I. I. Pigment Blue 22, C.I. I. Vat Blue 4, C.I. I. Vat Blue 6 etc. are mentioned. Of course, the present invention is not limited to these.

  Next, the dispersion resin used for the ink comprising the above-described carbon black constituting the ink set of the present invention will be described. In relation to the carbon black used in the ink, the relation between the adsorption amount A (g / g) of the dispersed resin and the DBP oil absorption amount B (g / g) is maintained at 0.2 ≦ A / B ≦ 0.6. Any one is possible as long as it is possible. Especially, an acid value of 20 mgKOH / g or more and 50 mgKOH / g or less is preferable. If the acid value is lower than 20 mgKOH / g, it may not be possible to secure the dispersion stability of the ink, which is not preferable. On the other hand, if the acid value is higher than 50 mgKOH / g, the hydrophilicity of the dispersion resin is increased, and the permeability to the recording medium is increased, which may lead to a decrease in the recording density of the recorded matter.

  In the present invention, it is preferable to use an amphiphilic block copolymer as the dispersion resin. Moreover, it is more preferable that the dispersion resin has a block structure having a hydrophobic block segment and a hydrophilic block segment. Furthermore, it is particularly preferable to use a block polymer having the following structure as the dispersion resin. That is, the block copolymer having a block structure in which the hydrophobic block segment A, the nonionic hydrophilic block segment B, and the ionic hydrophilic block segment C are arranged in the order of ABC is preferable.

  Further, when the degree of polymerization of the ABC block copolymer is 10 for the hydrophobic block segment A, the nonionic hydrophilic block segment B is 8 or less and the ionic hydrophilic block segment C is 5 or less. It is also a preferred form to use a certain copolymer. More preferably, when the degree of polymerization of the ABC block copolymer is 10 for the hydrophobic block segment A, the nonionic hydrophilic block segment B is 5 or less, and the ionic hydrophilic block segment C is 3 The following copolymer may be used. Here, the block copolymer used in 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.

  In the present invention, the block copolymer that can be used as the dispersion resin is not limited to the above, and a conventionally known block copolymer such as a block copolymer having a polyoxyethylene block is used. You can also. In the present invention, the block copolymer that can be used is more preferably in the form of a block such as AB, ABA or ABC. Here, A, B, and C indicate different block segments. In the present invention, the block copolymer may be a graft copolymer bonded to a certain copolymer chain in a T shape. In particular, in the present invention, it is preferable to use a block copolymer having a polyalkenyl ether structure as a repeating unit structure.

  In the present invention, a specific structure of an ionic block segment that can constitute a block polymer that can be used as a dispersion resin includes a repeating unit represented by the following general formula (1).

（上記式（１）中、Ｒ₀は、−Ｘ−ＣＯＯＨ、−Ｘ−ＣＯＯＭ、−Ｘ−ＣＨ(ＣＨ₂ＣＯＯＨ)₂、−Ｘ−ＣＨ(ＣＨ₂ＣＯＯＭ)₂、−Ｘ−ＣＨ(ＣＨ₂ＣＯＯ)₂Ｍ。−Ｘ−Ｏ−(ＣＨ₂)_q−ＣＯＯＨ、−Ｘ−Ｏ−(ＣＨ₂)_q−ＣＯＯＭ、−Ｘ−(Ｏ)_n−Ｐｈ−(ＣＨ₂)_q−ＣＯＯＨ、−Ｘ−(Ｏ)_n−Ｐｈ−(ＣＨ₂)_q−ＣＯＯＭを表す。ここで、−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キレン基を表す。ｎは１又は０を表す。ｑは０から１７の整数を表す。Ｍは、一価又は多価のカチオンを表す。）

(In the above formula (1), R ₀ is —X—COOH, —X—COOM, —X—CH (CH ₂ COOH) ₂ , —X—CH (CH ₂ COOM) ₂ , —X—CH (CH ₂ COO) ₂ M. —X—O— (CH ₂ ) _q —COOH, —X—O— (CH ₂ ) _q —COOM, —X— (O) _n —Ph— (CH ₂ ) _q —COOH, —X— (O) _n —Ph— (CH ₂ ) _q —COOM, wherein —X— represents a linear, branched or cyclic alkylene group having 1 to 20 carbon atoms. Represents 1 or 0. q represents an integer of 0 to 17. M represents a monovalent or polyvalent cation.)

  Specific examples of the repeating unit structure represented by the general formula (1) are given below. Note that Ph represents a phenylene group.

  Furthermore, in the present invention, the specific structure of the repeating unit of the hydrophobic block segment or nonionic hydrophilic block segment that can constitute the block polymer that can be used as the dispersion resin is represented by the following general formula (2). Repeating units.

（上記式（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、−Ｐｈ−Ｐｈ、−Ｎｐ、−（ＣＨ(Ｒ₅)−ＣＨ(Ｒ₆)−Ｏ)_p−Ｒ₇及び−(ＣＨ₂)_m−(Ｏ)_n−Ｒ₇からなる群から選ばれるものである。また、Ｒ₁において、芳香環中の水素原子は、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。また、ｐは１から１８の整数、ｍは１から３６の整数、ｎは０又は１である。Ｒ₅及びＲ₆は、それぞれ独立に、水素原子若しくは−ＣＨ₃である。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、−Ｐｈ−Ｐｈ、−Ｎｐ、−ＣＯ−ＣＨ＝ＣＨ₂、−ＣＯ−Ｃ(ＣＨ₃)＝ＣＨ₂、−ＣＨ₂ＣＯＯＲ₈からなる。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。Ｒ₈は、水素原子又は炭素数１から５のアルキル基である。なお、Ｐｈはフェニル基、Ｎｐはナフチル基を表わす。）

(In the above formula (2), R ₁ is a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, -Ph, -Ph-Ph, -Np,-(CH (R ₅ )- CH (R ₆ ) —O) _p —R ₇ and — (CH ₂ ) _m — (O) _n —R ₇ , and in R ₁ , the hydrogen atom in the aromatic ring is In addition, a linear or branched alkyl group having 1 to 4 carbon atoms and a carbon atom in the aromatic ring may be substituted with a nitrogen atom, respectively, and p is an integer of 1 to 18 , M is an integer from 1 to 36, and n is 0 or 1. R ₅ and R ₆ are each independently a hydrogen atom or —CH ₃ , R ₇ is a hydrogen atom, having 1 to 18 carbon atoms linear, branched or cyclic alkyl group, -Ph, -Ph-Ph, -Np , -CO-CH = CH 2, -CO-C (CH 3) = CH 2, -CH 2 Consisting OOR _8. Also, when R ₇ is other than hydrogen atom, the hydrogen atom bonded to a carbon atom in R ₇ is a linear or branched alkyl or -F 1 to 4 carbon atoms, -Cl, -Br, and a carbon atom in the aromatic ring can be substituted with a nitrogen atom, and R ₈ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, where Ph is (Phenyl group, Np represents a naphthyl group.)

  Specific examples of the hydrophobic block segment having a repeating unit structure represented by the general formula (2) include those described below. In addition, Ph represents a phenylene group and Np represents a naphthyl group.

  Specific examples of the nonionic hydrophilic block segment having the repeating unit structure represented by the general formula (2) shown above include those described below.

  Each block segment of the block copolymer that can be 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 that can be used in the present invention may be one in which the block copolymer structure is graft-bonded to another polymer.

  In the present invention, the content of the repeating unit structure represented by the general formula (1) or (2) contained in the block copolymer as described above is 0.01 mol% with respect to the entire block polymer. It is preferable that it is 99 mol% or less. More preferably, it is the range of 1 mol% or more and 90 mol% or less. 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.

  In the present invention, the block polymer preferably has a number average molecular weight (Mn) of 200 or more and 10,000,000 or less, and more preferably 1,000 or more and 1,000,000 or less. . When the number average molecular weight exceeds 10,000,000, the entanglement in the polymer chain and between the polymer chains becomes excessive, and it may be difficult to disperse in the solvent. On the other hand, when the number average molecular weight is less than 200, the molecular weight is small, and the steric effect as a polymer may be difficult to appear. In the present invention, the preferred degree of polymerization of each block segment of the hydrophobic block segment, nonionic hydrophilic block segment and ionic hydrophilic block segment constituting the block polymer is 3 or more and 10,000 or less. More preferably, they are 5 or more and 5,000 or less, More preferably, they are 10 or more and 4,000 or less.

  Further, in the ink constituting the ink set of the present invention, it is preferable to improve the dispersion stability and inclusion property (inclusive property) of the pigment. For this purpose, it is preferable that the molecular mobility of the block copolymer is made more flexible. That is, because the molecular mobility of the block copolymer is flexible, the block copolymer is easily entangled with the surface of the functional substance and easily becomes compatible. Furthermore, as will be described in detail later, when the ink is applied to the recording medium, the block copolymer is preferably flexible so that a coating layer can be easily formed on the recording medium. In order to make the block copolymer flexible, the glass transition temperature Tg of the main chain is preferably 20 ° C. or lower, more preferably 0 ° C. or lower, and further preferably −20 ° C. or lower. Also in these points, those having a polyalkenyl ether structure as the repeating unit of the block copolymer are generally preferably used in the present invention because they generally have a low glass transition point and flexible properties. In the case of the above repeating unit structure example, the glass transition temperature is often about −20 ° C. or lower.

In the present invention, the polymerization of the block copolymer having a polyalkenyl ether repeating unit structure that is preferably used can be carried out mainly by cationic polymerization. Examples of the initiator used at this time include protonic acids such as hydrochloric acid, sulfuric acid, methanesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and perchloric acid. Further, a combination of a Lewis acid such as BF ₃ , AlCl ₃ , TiCl ₄ , SnCl ₄ , FeCl ₃ , RAlCl ₂ , R _1.5 AlCl _1.5 (R represents alkyl) and a cation source can be used. Examples of the cation source include proton acids, water, alcohols, adducts of alkenyl ethers and carboxylic acids. By allowing these initiators to coexist with a polymerizable compound (monomer), the polymerization reaction proceeds, and a block copolymer can be synthesized. In the present invention, a suitable block copolymer having a polyalkenyl ether repeating unit structure is one containing a polyalkenyl ether repeating unit structure of 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more.

In the present invention, a more preferable polymerization method used for synthesizing a block copolymer to be suitably used will be described. Many methods for synthesizing polymers containing a polyalkenyl ether structure have been reported (see JP-A-11-080221). Among them, the method by cation living polymerization by Aoshima et al. (Polymer Bulletin, Vol. 15, 1986, page 417, JP-A-11-322942, JP-A-11-322866) is representative. By conducting polymer synthesis by cationic living polymerization, various polymers such as homopolymers, copolymers composed of two or more monomers, block copolymers, graft polymers, gradient polymers, etc. can be lengthened (molecular weight). It can be accurately aligned and synthesized. In addition, living polymerization can also be carried out in the HI / I ₂ system, HCl / SnCl ₄ system, or the like.

  As described above, as a method for preparing an ink containing a pigment such as carbon black, first, a resin and a pigment as a dispersant are added to an aqueous medium, mixed and stirred, and then dispersed using a dispersion means described later. Then, if necessary, a desired dispersion is obtained by performing centrifugation, filtration, or the like. The particle size (average dispersed particle size) of the pigment in the dispersion is not particularly limited, but the particle size is preferably 500 nm or less and 60 nm or more, more preferably 200 nm or less and 90 nm or more. By using a pigment having a particle diameter of 500 nm or less, the occurrence of clogging can be suppressed, and further sufficient ejection stability can be realized. On the other hand, when the particle size is less than 60 nm, the penetration of the pigment into the recording medium is accelerated, which may be undesirable. The average particle size of the pigment can be determined by a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, a laser Doppler method, or the like.

  In addition, in the method for producing an ink containing a pigment, it is effective to perform premixing before stirring and dispersing the aqueous medium containing the pigment. As an apparatus used in this case, a planetary stirrer that gives rotation and revolution is preferable. That is, such a premixing operation can improve the wettability of the pigment surface and promote the adsorption of the dispersant to the pigment surface.

  The disperser used in the above-described pigment dispersion treatment may be any commonly used disperser, and examples thereof include a sand mill, a pearl mill, a dyno mill, a ball mill, a roll mill, a nanomizer, and a homogenizer.

  Other components of the ink constituting the ink set of the present invention will be described. The ink used in the present invention may contain a water-soluble organic solvent as listed below as necessary. In the present invention, examples of the water-soluble organic solvent preferably used include the following. Alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.). Polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol. Hexanediol, pentanediol, glycerin, diglycerin, hexanetriol, thiodiglycol, etc. ). Polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether. Diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl Ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether). Amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine. Triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyl Diethylenetriamine, tetramethylpropylenediamine, etc.). Amides (for example, formamide, N, N-dimethylformamide, N, N-dimethylacetamide and the like). Heterocycles (eg 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone). Sulfoxides (for example, dimethyl sulfoxide). Sulfones (for example, sulfolane), urea, acetonitrile, acetone and the like. Although there is no restriction | limiting in particular about content of the said water-soluble organic solvent in the ink used for this invention, 5 mass% or more and 60 mass% or less of the total mass of an ink, More preferably, 5 mass% or more and 40 mass% or less Is a preferred range.

  The ink used in the present invention may be adjusted for surface tension by adding a surfactant as necessary. The surface tension is preferably 40 mN / m or less from the viewpoint of ink permeability. By setting it to 40 mN / m or less, the penetrability of the ink into the recording medium is increased, and the fixing property during high-speed printing is improved. Examples of the surfactant preferably used in this case include the following. Anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates and fatty acid salts. Nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxyethylene / polyoxypropylene block copolymers. Examples include cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used. Furthermore, acetylene glycols are preferable.

  The ink used in the present invention may contain a pH buffer as necessary. The pH buffer solution is not particularly limited as long as it is a buffering agent capable of adjusting the ink to pH 7 to pH 10. Specific examples include potassium hydrogen phthalate, potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium tetraborate, potassium hydrogen tartrate, sodium bicarbonate, sodium carbonate. Examples thereof include tris (hydroxymethyl) aminomethane and tris (hydroxymethyl) aminomethane hydrochloride. The content of the pH buffering agent is preferably such that the pH of the ink is approximately pH 7 to pH 10 from the viewpoint of durability of the head member and ink stability.

  In addition to this, the ink used in the present invention may contain a preservative, an antifungal agent, an antifoaming agent, a moisturizing agent, a viscosity adjusting agent, and the like, if necessary. In the case of containing a humectant, saccharides are preferable, and examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. Preferably, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glycidyl, sorbit, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose and the like can be mentioned.

<Reaction solution>
Next, the reaction liquid that constitutes the ink set according to the present invention together with the above-described ink will be described. The reaction liquid used in the present invention contains a reactive substance having reactivity with the dispersion resin in the ink described above, and a most preferable reactive substance is a polyvalent metal salt. The polyvalent metal salt is composed of a divalent or higher polyvalent metal ion and an anion that binds to these polyvalent metal ions. Specific 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 metals such as Fe ³⁺ and Al ^3+. Ions. Examples of the anion include Cl ⁻ , COO ⁻ , NO ₃ ⁻ , SO ₄ ^{2− and the} like. In the present invention, the reaction liquid preferably contains 1% by mass or more of a polyvalent metal salt based on the total mass of the reaction liquid in order to instantaneously react the ink and the reaction liquid to form an aggregated film. .

  In the present invention, examples of the water-soluble organic solvent that can be used in the reaction solution include the following. Alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.). Polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol. Propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, diglycerin, hexanetriol, thiodiglycol, etc. ). Polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether. Diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl Ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether). Amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine. Triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyl Diethylenetriamine, tetramethylpropylenediamine, etc.). Amides (for example, formamide, N, N-dimethylformamide, N, N-dimethylacetamide and the like). Heterocycles (eg 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone). Examples thereof include sulfoxides (for example, dimethyl sulfoxide), sulfones (for example, sulfolane), urea, acetonitrile, acetone and the like. In the present invention, the content of the water-soluble organic solvent in the reaction solution is not particularly limited, but is 5% by mass to 60% by mass, more preferably 5% by mass to 40% by mass, based on the total mass of the reaction solution. % Or less is a suitable range.

  In addition to the above, the reaction solution used in the present invention may further contain additives such as a viscosity adjuster, a pH adjuster, a preservative, and an antioxidant as necessary. The surfactant that functions as a penetration accelerator is preferably added so that the surface tension of the reaction solution is 30 mN / m or more and 40 mN / m or less. Further, the reaction liquid used in the present invention is more preferably colorless, but it may be light in a range that does not change the color tone of each color ink when mixed with ink on the recording medium.

<Inkjet recording method>
The inkjet recording method of the present invention includes a step of applying a reaction liquid constituting the ink set of the present invention onto a recording medium, and a step of applying an ink constituting the ink set of the present invention onto a recording medium. Then, the reaction liquid and the ink are brought into contact with each other on a recording medium to form an image. As described above, in the ink jet recording method in which the ink set having the ink and the reaction liquid is separately used and these are applied onto the recording medium, the following various recording methods can be considered. It is done.
a: When printing ink after printing reaction liquid b: When printing reaction liquid after printing ink c: When printing reaction liquid after printing ink and further printing ink d: Printing reaction liquid In the case where the ink is printed and the reaction liquid is further printed, the recording method of the ink and the reaction liquid may be appropriately selected. However, in view of the object of the present invention, a or d including at least a step of recording the reaction liquid on the recording medium prior to the ink is preferable.

  In the inkjet recording method of a or d, first, a reaction liquid is applied to a recording medium, and then ink is applied to a site to which the reaction liquid is applied. For this reason, the color material in the ink can be retained on the surface of the recording medium by reacting with the reaction liquid present on the surface of the recording medium immediately after being applied to the recording medium. . As a result, it is considered that the recording density of the recorded matter is improved.

  The ink set according to each of the above embodiments is suitably used as an ink set for inkjet recording. As an ink jet recording method, there are a recording method in which mechanical energy is applied to ink to eject droplets, and a recording method in which thermal energy is applied to ink and ink droplets are ejected by foaming of the ink. The ink set of the present invention is particularly suitable for these ink jet recording methods.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In the text, “parts” and “%” are based on mass unless otherwise specified. In addition, the “remainder” described in the text means that the total amount of each ink or each reaction liquid described below is 100% or 100 parts, and from this, the sum of the amount of the composition in which the specific amount is described. The remainder after deduction.

[Method of synthesizing dispersion resin]
<Synthesis example 1 (dispersion resin A)>
Dispersion resin A, which is a ternary block copolymer composed of block segments A, B and C composed of the following repeating units, was synthesized by living cation polymerization using an aluminum catalyst by the method described below.

(1) Hydrophobic block segment A:

(2) Nonionic hydrophilic block segment B:

(3) Ionic hydrophilic block segment C:

  Specifically, first, the inside of a glass container equipped with a three-way cock used for the synthesis of a block polymer was purged with nitrogen, and then heated to 250 ° C. in a nitrogen gas atmosphere to remove adsorbed water. Thereafter, the system is returned to room temperature, and 5.0 mmol of monomer components which are repeating units constituting the hydrophobic block segment, which is the A block, 16 mmol of ethyl acetate, 0.05 mmol of 1-isobutoxyethyl acetate, and 11 ml of toluene are added to react. The 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 using time-resolved molecular sieve column chromatography (GPC) to confirm the completion of A block polymerization.

  Next, 1.2 mmol of the monomer as the above-mentioned repeating unit constituting the nonionic hydrophilic block segment which is the B block was added, and the polymerization was continued. As described above, the completion of polymerization of the B block was confirmed by monitoring using GPC. Then, the toluene solution of the ethyl ester body used as the monomer component which becomes the above-mentioned repeating unit which comprises the ionic hydrophilic block segment which is 1 mmol said C block was added to these, and superposition | polymerization was continued. The polymerization reaction was stopped when the polymerization of the monomer component proceeded 10 units. 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 obtained organic phase was concentrated and dried with an evaporator, and further vacuum-dried, 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. The compound was identified using NMR and GPC.

  Furthermore, the triblock polymer obtained above was hydrolyzed in a mixed solution of dimethylformamide and aqueous sodium hydroxide to produce a triblock polymer in which the C block component was hydrolyzed to form sodium chloride. The compound was identified using NMR and GPC. Furthermore, the dispersion resin A, which is a triblock polymer in which the C block component is 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. The acid value of the obtained dispersion resin A was 40 mgKOH / g.

<Synthesis example 2 (dispersion resin B)>
A dispersion resin B, which is a ternary block copolymer, was obtained in the same manner as in Synthesis Example 1 except that block segments A, B, and C consisting of the following repeating units were used. The acid value of the obtained dispersion resin B was 72 mgKOH / g.

(1) Hydrophobic block segment A:

(2) Nonionic hydrophilic block segment B:

(3) Ionic hydrophilic block segment C:

<Synthesis Example 3 (Dispersion Resin C)>
Dispersing resin C which is a binary block copolymer composed of block segments A and B composed of the following repeating units was obtained by known living anionic polymerization. The obtained dispersion resin C had an acid value of 89 mgKOH / g.
(1) Hydrophobic block segment A:

(3) Ionic hydrophilic block segment B:

<Synthesis example 4 (dispersion resin D)>
A dispersion resin D, which is a binary random copolymer having the following repeating units, was obtained by known radical polymerization. The acid value of the obtained dispersion resin D was 79 mgKOH / g.

(1) Hydrophobic repeating unit A:

(3) Ionic hydrophilic repeating unit B:

[Preparation method of Black pigment dispersion]
A 500 mL eggplant flask equipped with a mechanical stirrer was placed in a tank of an ultrasonic generator, and each dispersion resin obtained as described above and carbon black described later were placed therein. Furthermore, 120 mL of tetrahydrofuran was added and mixed well with a planetary stirrer (manufactured by Kurabo Industries) until the pigment surface was sufficiently wet with the solvent. Next, the phase was reversed by dropping and injecting an alkaline aqueous solution containing KOH (potassium hydroxide) so that the neutralization rate of the used dispersion resin was 100%. Thereafter, premixing was performed for 60 minutes, and dispersion was performed for 5 hours using a nanomizer YSNM-2000AR (manufactured by Yoshida Kikai Kogyo Co., Ltd.). Tetrahydrofuran was distilled off from this dispersion using a rotary evaporator, and the concentration was adjusted to obtain a pigment dispersion having a pigment concentration of 6%. Using the obtained Black pigment dispersion, CHDF2000 (manufactured by Matec Applied Sciences) was used to calculate the amount of dispersion resin adsorbed per gram of carbon black.

[Ink preparation method]
Inks 1 to 16 were prepared using each Black pigment dispersion obtained above, glycerin, diethylene glycol, trimethylolpropane, acetylenol EH (manufactured by Kawaken Fine Chemical Co., Ltd.), and ion-exchanged water. At that time, one of the following ink compositions a and b was selected to prepare each ink. In addition, the pH of each of the inks 1 to 16 is adjusted to 9.5 using KOH.

(Ink composition a)
・ Black pigment dispersion 67 parts ・ Diethylene glycol 5 parts ・ Glycerin 7 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH 0.5 part ・ Ion-exchanged water balance

(Ink composition b)
・ Black pigment dispersion 67 parts ・ Diethylene glycol 5 parts ・ Glycerin 7 parts ・ Trimethylolpropane 7 parts ・ Acetylenol EH 0.2 part ・ Ion-exchanged water balance

<Ink 1>
Dispersion resin A and carbon black Color Black FW18 (manufactured by Degussa) obtained above were dispersed by the above-described Black pigment dispersion preparation method to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the ink composition a to prepare ink 1 used in the ink set of Example 1.

<Ink 2>
Dispersion resin A and carbon black Printex L6 (manufactured by Degussa) obtained above were dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 4%. Next, this was blended with the above ink composition a to prepare ink 2 used in the ink set of Example 2.

<Ink 3>
Dispersion resin A and carbon black Monarch 700 (manufactured by Cabot Special Chemicals) obtained above are dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 4%. It was. Subsequently, this was blended with the ink composition a to prepare ink 3 used for the ink set of Example 3.

<Ink 4>
Dispersion resin B and carbon black Printex L6 (manufactured by Degussa) obtained above were dispersed by the above-described method for producing a Black pigment dispersion to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the ink composition a to prepare ink 4 used in the ink set of Example 4.

<Ink 5>
Dispersion resin C and carbon black Printex L6 (manufactured by Degussa) obtained above were dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the ink composition a to prepare ink 5 used in the ink set of Example 5.

<Ink 6>
Dispersion resin D and carbon black Printex L6 (manufactured by Degussa) obtained above were dispersed by the above-described method for producing a Black pigment dispersion to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the above ink composition a to prepare ink 6 used in the ink set of Example 6.

<Ink 7>
Dispersion resin A and carbon black Color Black FW18 (manufactured by Degussa) obtained above were dispersed by the above-described Black pigment dispersion preparation method to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the ink composition b to prepare ink 7 used in the ink set of Example 7.

<Ink 8>
Dispersion resin A and carbon black Printex L6 (manufactured by Degussa) obtained above were dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the ink composition b to prepare ink 8 used in the ink set of Example 8.
The compositions and physical properties of the inks 1 to 8 obtained as described above are summarized in Table 1.

<Ink 9>
Dispersion resin C and carbon black Monarch 800 (manufactured by Cabot Special Chemicals) obtained above are dispersed by the above-described Black pigment dispersion preparation method to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 4%. It was. Next, this was blended with the ink composition a to prepare ink 9 used in the ink set of Comparative Example 1.

<Ink 10>
Dispersion resin C obtained above, carbon black No. 2300 (manufactured by Mitsubishi Kasei) was dispersed by the above-described method for producing a Black pigment dispersion to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 6%. Subsequently, this was blended with the ink composition a to prepare an ink for use in the ink set of Comparative Example 2.

<Ink 11>
Dispersion resin C and carbon black Printex 95 (manufactured by Degussa) obtained above were dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the ink composition a to prepare ink 11 used in the ink set of Comparative Example 3.

<Ink 12>
Dispersion resin C obtained above, carbon black No. 2600 (manufactured by Mitsubishi Kasei) was dispersed by the above-described method for producing a Black pigment dispersion to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 4%. Subsequently, this was blended with the ink composition a to prepare ink 12 used in the ink set of Comparative Example 4.

<Ink 13>
Dispersion resin C obtained above, carbon black No. 2600 (manufactured by Mitsubishi Kasei Co., Ltd.) was dispersed by the above-described method for producing a Black pigment dispersion to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 6%. Subsequently, this was blended with the ink composition a to prepare ink 13 used in the ink set of Comparative Example 5.

<Ink 14>
Dispersion resin D and carbon black Monarch 700 (manufactured by Cabot Special Chemicals) obtained above are dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 6%. It was. Subsequently, this was blended with the ink composition a to prepare an ink 14 used in the ink set of Comparative Example 6.

<Ink 15>
Dispersion resin D and carbon black Monarch 700 (manufactured by Cabot Special Chemicals) obtained above are dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion having a pigment concentration of 6% and a resin concentration of 6%. It was. Subsequently, this was blended with the ink composition b to prepare ink 15 used for the ink set of Comparative Example 7.

<Ink 16>
Dispersion resin D and carbon black Color Black FW18 (manufactured by Degussa) obtained above were dispersed by the above-described method for preparing a Black pigment dispersion to obtain a Black pigment dispersion with a pigment concentration of 6% and a resin concentration of 1%. Next, this was blended with the ink composition a to prepare ink 16 used for the ink set of Comparative Example 8.
The compositions and physical properties of the inks 9 to 16 obtained as described above are summarized in Table 2.

[Preparation of reaction solution]
A reaction solution having the following composition was prepared using Mg nitrate and glycerin, ethylene glycol, diethylene glycol, urea, isopropanol, acetylenol EH (manufactured by Kawaken Fine Chemical Co., Ltd.), and ion-exchanged water. Note that the pH of the reaction solution is adjusted to 7.0.

(Reaction solution)
-Mg nitrate 10%
・ Glycerin 7.0%
・ Ethylene glycol 5.0%
・ Diethylene glycol 3.0%
・ Urea 9%
・ Isopropanol 2.5%
・ Acetylenol EH 0.6%
・ Ion exchange water balance

[Preparation of ink set]
Inks 1 to 16 obtained above were combined with the reaction liquid obtained above to prepare ink sets of Examples 1 to 8 and Comparative Examples 1 to 8, respectively.

[Evaluation of ink set]
(Preparation of evaluation sample)
The ink sets of Examples 1 to 8 and Comparative Examples 1 to 8 thus obtained were evaluated for OD (recording density), quick drying property, scratch resistance, and marker resistance as follows. For the evaluation of each ink set, an ink jet printer BJF-930 (manufactured by Canon Inc.) was used, and the ink and the reaction liquid constituting each of the ink sets were mounted separately for each ink set. Next, each loaded reaction solution was printed on PB paper (manufactured by Canon Inc.), which is plain paper, at 25% duty, and each loaded ink was printed at 100% duty. An ink set evaluation sample was prepared.

(OD evaluation)
24 hours after the end of ink printing, the OD of the printed portion of each evaluation sample was measured using RD-19 (manufactured by Gretag Macbeth). The measurement results are shown in Tables 3 and 4.

(Quick-drying evaluation)
Immediately after ink printing and 5 minutes after the completion of ink printing, plain paper was pressed against the printed surface of each evaluation sample, and quick-drying evaluation was performed by observing the ink transfer of the black solid portion onto the plain paper. The evaluation criteria for quick drying are as follows, and the evaluation results are shown in Tables 3 and 4.
○: No ink transfer ×: Ink transfer

(Abrasion resistance evaluation)
Scratch resistance was evaluated by rubbing the black solid portion of each evaluation sample with a finger 5 minutes after the completion of ink printing and 1 hour after the completion of ink printing, and observing the presence or absence of ink transfer to the finger. The evaluation criteria of the scratch resistance are as follows, and the evaluation results are shown in Tables 3 and 4.
○: No ink transfer ×: Ink transfer

(Marker resistance evaluation)
The marker resistance was evaluated by tracing the black solid portion of each evaluation sample with a fluorescent marker 5 minutes after completion of ink printing and 1 hour after completion of ink printing, and observing the presence or absence of ink bleeding. The evaluation criteria of marker resistance are as follows, and the evaluation results are shown in Tables 3 and 4.
○: No ink smearing ×: Ink smearing

  From the above evaluation results, the relationship between the adsorption amount A (g / g) of the dispersed resin per gram of carbon black and the DBP oil absorption amount B (g / g) per gram of carbon black is 0.2 ≦ A / B ≦. Use ink that satisfies the relationship of 0.6. Furthermore, it has been shown that the following excellent effects can be obtained by using this ink in combination with a reaction liquid containing a reactive substance having reactivity with the dispersion resin in the ink. In other words, it was shown that a high-speed printing can be performed on plain paper, and a recorded matter excellent in scratch resistance and marker resistance can be obtained while maintaining a high recording density.

Claims (10)

  In an ink set having independently a recording liquid containing at least a dispersion resin and carbon black and a reaction liquid containing a reactive substance having reactivity with the dispersion resin, the dispersion resin per 1 g of the carbon black The relationship between the adsorption amount A (g / g) adsorbed by and the DBP oil absorption amount B (g / g) per 1 g of the carbon black is 0.2 ≦ A / B ≦ 0.6, Ink set for inkjet recording.   The ink set for inkjet recording according to claim 1, wherein the surface tension of the recording liquid is 40 mN / m or less.   The ink set for inkjet recording according to claim 1 or 2, wherein the acid value of the dispersion resin is 20 mgKOH / g or more and 50 mgKOH / g or less.   The ink set for inkjet recording according to any one of claims 1 to 3, wherein a DBP oil absorption B per 1 g of the carbon black is 1.0 g / g or more.   The ink set for inkjet recording according to any one of claims 1 to 4, wherein the reaction solution contains 1% by mass or more of a polyvalent metal salt as a reactive substance.   The ink set for inkjet recording according to any one of claims 1 to 5, wherein the dispersion resin is an amphiphilic block copolymer.   The ink set for inkjet recording according to any one of claims 1 to 6, wherein the dispersion resin has a block structure including a hydrophobic block segment and a hydrophilic block segment.   8. The block copolymer according to claim 1, wherein the dispersion resin is a block copolymer having a block structure in which a hydrophobic block segment, a nonionic hydrophilic block segment, and an ionic hydrophilic block segment are arranged in order. The ink set for inkjet recording as described.   The ink set for inkjet recording according to any one of claims 1 to 8, wherein the dispersion resin is a block copolymer having a polyalkenyl ether structure as a repeating unit structure.   A step of applying a reaction liquid constituting the ink set for inkjet recording according to any one of claims 1 to 9 onto a recording medium, and the inkjet recording according to any one of claims 1 to 9. An ink jet recording method comprising a step of applying a recording liquid constituting an ink set onto a recording medium, and forming an image by bringing the reaction liquid and the recording liquid into contact with each other on the recording medium.